From 8a60985363b537abdab9df8d32b59bb3d4c9ae8f Mon Sep 17 00:00:00 2001
From: Michael Lamothe <michael.lamothe@gmail.com>
Date: Sat, 4 Jan 2025 19:39:06 +1100
Subject: [PATCH] Upgraded to .NET 8 and made code style a little more
 internally consistent. (#1680)

---
 dotnet-examples/Common/Common.csproj          |   2 +-
 dotnet-examples/Common/WaveHeader.cs          | 281 +++++++++---------
 .../keyword-spotting-from-files/Program.cs    |  12 +-
 .../keyword-spotting-from-files.csproj        |   2 +-
 .../Program.cs                                |  27 +-
 .../keyword-spotting-from-microphone.csproj   |   2 +-
 .../offline-decode-files/Program.cs           |  71 +++--
 .../offline-decode-files.csproj               |   2 +-
 .../offline-punctuation/Program.cs            |   6 +-
 .../offline-punctuation.csproj                |   2 +-
 .../offline-speaker-diarization/Program.cs    |  13 +-
 .../offline-speaker-diarization.csproj        |   2 +-
 dotnet-examples/offline-tts-play/Program.cs   |  47 ++-
 .../offline-tts-play/offline-tts-play.csproj  |   2 +-
 dotnet-examples/offline-tts/Program.cs        |  37 ++-
 .../offline-tts/offline-tts.csproj            |   2 +-
 .../online-decode-files/Program.cs            |  44 ++-
 .../online-decode-files.csproj                |   2 +-
 dotnet-examples/sherpa-onnx.sln               |   8 +-
 .../speaker-identification/Program.cs         |  26 +-
 .../speaker-identification.csproj             |   2 +-
 .../Program.cs                                |  44 ++-
 .../speech-recognition-from-microphone.csproj |   2 +-
 .../spoken-language-identification/Program.cs |   5 +-
 .../spoken-language-identification.csproj     |   2 +-
 .../streaming-hlg-decoding/Program.cs         |  17 +-
 .../streaming-hlg-decoding.csproj             |   2 +-
 .../Program.cs                                |  54 ++--
 .../vad-non-streaming-asr-paraformer.csproj   |   2 +-
 29 files changed, 335 insertions(+), 385 deletions(-)

diff --git a/dotnet-examples/Common/Common.csproj b/dotnet-examples/Common/Common.csproj
index a9630614f..57c0ff743 100644
--- a/dotnet-examples/Common/Common.csproj
+++ b/dotnet-examples/Common/Common.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net6.0</TargetFramework>
+        <TargetFramework>net8.0</TargetFramework>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     </PropertyGroup>
     <ItemGroup>
diff --git a/dotnet-examples/Common/WaveHeader.cs b/dotnet-examples/Common/WaveHeader.cs
index 7d13b3553..0a6ca5284 100644
--- a/dotnet-examples/Common/WaveHeader.cs
+++ b/dotnet-examples/Common/WaveHeader.cs
@@ -4,171 +4,166 @@
 
 using System.Runtime.InteropServices;
 
-namespace SherpaOnnx
-{
+namespace SherpaOnnx;
 
-  [StructLayout(LayoutKind.Sequential)]
-  public struct WaveHeader
+[StructLayout(LayoutKind.Sequential)]
+public struct WaveHeader
+{
+  public int ChunkID;
+  public int ChunkSize;
+  public int Format;
+  public int SubChunk1ID;
+  public int SubChunk1Size;
+  public short AudioFormat;
+  public short NumChannels;
+  public int SampleRate;
+  public int ByteRate;
+  public short BlockAlign;
+  public short BitsPerSample;
+  public int SubChunk2ID;
+  public int SubChunk2Size;
+
+  public bool Validate()
   {
-    public Int32 ChunkID;
-    public Int32 ChunkSize;
-    public Int32 Format;
-    public Int32 SubChunk1ID;
-    public Int32 SubChunk1Size;
-    public Int16 AudioFormat;
-    public Int16 NumChannels;
-    public Int32 SampleRate;
-    public Int32 ByteRate;
-    public Int16 BlockAlign;
-    public Int16 BitsPerSample;
-    public Int32 SubChunk2ID;
-    public Int32 SubChunk2Size;
-
-    public bool Validate()
+    if (ChunkID != 0x46464952)
+    {
+      Console.WriteLine($"Invalid chunk ID: 0x{ChunkID:X}. Expect 0x46464952");
+      return false;
+    }
+
+    //               E V A W
+    if (Format != 0x45564157)
+    {
+      Console.WriteLine($"Invalid format: 0x{Format:X}. Expect 0x45564157");
+      return false;
+    }
+
+    //                      t m f
+    if (SubChunk1ID != 0x20746d66)
+    {
+      Console.WriteLine($"Invalid SubChunk1ID: 0x{SubChunk1ID:X}. Expect 0x20746d66");
+      return false;
+    }
+
+    if (SubChunk1Size != 16)
+    {
+      Console.WriteLine($"Invalid SubChunk1Size: {SubChunk1Size}. Expect 16");
+      return false;
+    }
+
+    if (AudioFormat != 1)
+    {
+      Console.WriteLine($"Invalid AudioFormat: {AudioFormat}. Expect 1");
+      return false;
+    }
+
+    if (NumChannels != 1)
+    {
+      Console.WriteLine($"Invalid NumChannels: {NumChannels}. Expect 1");
+      return false;
+    }
+
+    if (ByteRate != (SampleRate * NumChannels * BitsPerSample / 8))
+    {
+      Console.WriteLine($"Invalid byte rate: {ByteRate}.");
+      return false;
+    }
+
+    if (BlockAlign != (NumChannels * BitsPerSample / 8))
     {
-      if (ChunkID != 0x46464952)
-      {
-        Console.WriteLine($"Invalid chunk ID: 0x{ChunkID:X}. Expect 0x46464952");
-        return false;
-      }
-
-      //               E V A W
-      if (Format != 0x45564157)
-      {
-        Console.WriteLine($"Invalid format: 0x{Format:X}. Expect 0x45564157");
-        return false;
-      }
-
-      //                      t m f
-      if (SubChunk1ID != 0x20746d66)
-      {
-        Console.WriteLine($"Invalid SubChunk1ID: 0x{SubChunk1ID:X}. Expect 0x20746d66");
-        return false;
-      }
-
-      if (SubChunk1Size != 16)
-      {
-        Console.WriteLine($"Invalid SubChunk1Size: {SubChunk1Size}. Expect 16");
-        return false;
-      }
-
-      if (AudioFormat != 1)
-      {
-        Console.WriteLine($"Invalid AudioFormat: {AudioFormat}. Expect 1");
-        return false;
-      }
-
-      if (NumChannels != 1)
-      {
-        Console.WriteLine($"Invalid NumChannels: {NumChannels}. Expect 1");
-        return false;
-      }
-
-      if (ByteRate != (SampleRate * NumChannels * BitsPerSample / 8))
-      {
-        Console.WriteLine($"Invalid byte rate: {ByteRate}.");
-        return false;
-      }
-
-      if (BlockAlign != (NumChannels * BitsPerSample / 8))
-      {
-        Console.WriteLine($"Invalid block align: {ByteRate}.");
-        return false;
-      }
-
-      if (BitsPerSample != 16)
-      {  // we support only 16 bits per sample
-        Console.WriteLine($"Invalid bits per sample: {BitsPerSample}. Expect 16");
-        return false;
-      }
-
-      return true;
+      Console.WriteLine($"Invalid block align: {ByteRate}.");
+      return false;
     }
+
+    if (BitsPerSample != 16)
+    {  // we support only 16 bits per sample
+      Console.WriteLine($"Invalid bits per sample: {BitsPerSample}. Expect 16");
+      return false;
+    }
+
+    return true;
   }
+}
 
-  // It supports only 16-bit, single channel WAVE format.
-  // The sample rate can be any value.
-  public class WaveReader
+// It supports only 16-bit, single channel WAVE format.
+// The sample rate can be any value.
+public class WaveReader
+{
+  public WaveReader(string fileName)
   {
-    public WaveReader(String fileName)
+    if (!File.Exists(fileName))
     {
-      if (!File.Exists(fileName))
-      {
-        throw new ApplicationException($"{fileName} does not exist!");
-      }
-
-      using (var stream = File.Open(fileName, FileMode.Open))
-      {
-        using (var reader = new BinaryReader(stream))
-        {
-          _header = ReadHeader(reader);
-
-          if (!_header.Validate())
-          {
-            throw new ApplicationException($"Invalid wave file ${fileName}");
-          }
-
-          SkipMetaData(reader);
-
-          // now read samples
-          // _header.SubChunk2Size contains number of bytes in total.
-          // we assume each sample is of type int16
-          byte[] buffer = reader.ReadBytes(_header.SubChunk2Size);
-          short[] samples_int16 = new short[_header.SubChunk2Size / 2];
-          Buffer.BlockCopy(buffer, 0, samples_int16, 0, buffer.Length);
-
-          _samples = new float[samples_int16.Length];
-
-          for (var i = 0; i < samples_int16.Length; ++i)
-          {
-            _samples[i] = samples_int16[i] / 32768.0F;
-          }
-        }
-      }
+      throw new ApplicationException($"{fileName} does not exist!");
     }
 
-    private static WaveHeader ReadHeader(BinaryReader reader)
-    {
-      byte[] bytes = reader.ReadBytes(Marshal.SizeOf(typeof(WaveHeader)));
+    using var stream = File.Open(fileName, FileMode.Open);
+    using var reader = new BinaryReader(stream);
 
-      GCHandle handle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
-      WaveHeader header = (WaveHeader)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(WaveHeader))!;
-      handle.Free();
+    _header = ReadHeader(reader);
 
-      return header;
+    if (!_header.Validate())
+    {
+      throw new ApplicationException($"Invalid wave file ${fileName}");
     }
 
-    private void SkipMetaData(BinaryReader reader)
+    SkipMetaData(reader);
+
+    // now read samples
+    // _header.SubChunk2Size contains number of bytes in total.
+    // we assume each sample is of type int16
+    var buffer = reader.ReadBytes(_header.SubChunk2Size);
+    var samples_int16 = new short[_header.SubChunk2Size / 2];
+    Buffer.BlockCopy(buffer, 0, samples_int16, 0, buffer.Length);
+
+    _samples = new float[samples_int16.Length];
+
+    for (var i = 0; i < samples_int16.Length; ++i)
     {
-      var bs = reader.BaseStream;
-
-      Int32 subChunk2ID = _header.SubChunk2ID;
-      Int32 subChunk2Size = _header.SubChunk2Size;
-
-      while (bs.Position != bs.Length && subChunk2ID != 0x61746164)
-      {
-        bs.Seek(subChunk2Size, SeekOrigin.Current);
-        subChunk2ID = reader.ReadInt32();
-        subChunk2Size = reader.ReadInt32();
-      }
-      _header.SubChunk2ID = subChunk2ID;
-      _header.SubChunk2Size = subChunk2Size;
+      _samples[i] = samples_int16[i] / 32768.0F;
     }
+  }
 
-    private WaveHeader _header;
+  private static WaveHeader ReadHeader(BinaryReader reader)
+  {
+    var bytes = reader.ReadBytes(Marshal.SizeOf(typeof(WaveHeader)));
+
+    GCHandle handle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
+    WaveHeader header = (WaveHeader)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(WaveHeader))!;
+    handle.Free();
+
+    return header;
+  }
 
-    // Samples are normalized to the range [-1, 1]
-    private float[] _samples;
+  private void SkipMetaData(BinaryReader reader)
+  {
+    var bs = reader.BaseStream;
 
-    public int SampleRate => _header.SampleRate;
-    public float[] Samples => _samples;
+    var subChunk2ID = _header.SubChunk2ID;
+    var subChunk2Size = _header.SubChunk2Size;
 
-    public static void Test(String fileName)
+    while (bs.Position != bs.Length && subChunk2ID != 0x61746164)
     {
-      WaveReader reader = new WaveReader(fileName);
-      Console.WriteLine($"samples length: {reader.Samples.Length}");
-      Console.WriteLine($"samples rate: {reader.SampleRate}");
+      bs.Seek(subChunk2Size, SeekOrigin.Current);
+      subChunk2ID = reader.ReadInt32();
+      subChunk2Size = reader.ReadInt32();
     }
+    _header.SubChunk2ID = subChunk2ID;
+    _header.SubChunk2Size = subChunk2Size;
   }
 
+  private WaveHeader _header;
+
+  // Samples are normalized to the range [-1, 1]
+  private float[] _samples;
+
+  public int SampleRate => _header.SampleRate;
+
+  public float[] Samples => _samples;
+
+  public static void Test(string fileName)
+  {
+    WaveReader reader = new WaveReader(fileName);
+    Console.WriteLine($"samples length: {reader.Samples.Length}");
+    Console.WriteLine($"samples rate: {reader.SampleRate}");
+  }
 }
diff --git a/dotnet-examples/keyword-spotting-from-files/Program.cs b/dotnet-examples/keyword-spotting-from-files/Program.cs
index 2fea260d1..00ba3777a 100644
--- a/dotnet-examples/keyword-spotting-from-files/Program.cs
+++ b/dotnet-examples/keyword-spotting-from-files/Program.cs
@@ -13,8 +13,6 @@
 // dotnet run
 
 using SherpaOnnx;
-using System.Collections.Generic;
-using System;
 
 class KeywordSpotterDemo
 {
@@ -38,11 +36,11 @@ static void Main(string[] args)
 
     var filename = "./sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01/test_wavs/3.wav";
 
-    WaveReader waveReader = new WaveReader(filename);
+    var waveReader = new WaveReader(filename);
 
     Console.WriteLine("----------Use pre-defined keywords----------");
 
-    OnlineStream s = kws.CreateStream();
+    var s = kws.CreateStream();
     s.AcceptWaveform(waveReader.SampleRate, waveReader.Samples);
 
     float[] tailPadding = new float[(int)(waveReader.SampleRate * 0.3)];
@@ -53,7 +51,7 @@ static void Main(string[] args)
     {
       kws.Decode(s);
       var result = kws.GetResult(s);
-      if (result.Keyword != "")
+      if (result.Keyword != string.Empty)
       {
         Console.WriteLine("Detected: {0}", result.Keyword);
       }
@@ -70,7 +68,7 @@ static void Main(string[] args)
     {
       kws.Decode(s);
       var result = kws.GetResult(s);
-      if (result.Keyword != "")
+      if (result.Keyword != string.Empty)
       {
         Console.WriteLine("Detected: {0}", result.Keyword);
       }
@@ -89,7 +87,7 @@ static void Main(string[] args)
     {
       kws.Decode(s);
       var result = kws.GetResult(s);
-      if (result.Keyword != "")
+      if (result.Keyword != string.Empty)
       {
         Console.WriteLine("Detected: {0}", result.Keyword);
       }
diff --git a/dotnet-examples/keyword-spotting-from-files/keyword-spotting-from-files.csproj b/dotnet-examples/keyword-spotting-from-files/keyword-spotting-from-files.csproj
index 992f8e0e3..21b9d3ea5 100644
--- a/dotnet-examples/keyword-spotting-from-files/keyword-spotting-from-files.csproj
+++ b/dotnet-examples/keyword-spotting-from-files/keyword-spotting-from-files.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>keyword_spotting_from_files</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/keyword-spotting-from-microphone/Program.cs b/dotnet-examples/keyword-spotting-from-microphone/Program.cs
index cb0c922f4..05d22aee0 100644
--- a/dotnet-examples/keyword-spotting-from-microphone/Program.cs
+++ b/dotnet-examples/keyword-spotting-from-microphone/Program.cs
@@ -12,12 +12,9 @@
 //
 // dotnet run
 
+using PortAudioSharp;
 using SherpaOnnx;
-using System.Collections.Generic;
 using System.Runtime.InteropServices;
-using System;
-
-using PortAudioSharp;
 
 class KeywordSpotterDemo
 {
@@ -41,11 +38,11 @@ static void Main(string[] args)
 
     var filename = "./sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01/test_wavs/3.wav";
 
-    WaveReader waveReader = new WaveReader(filename);
+    var waveReader = new WaveReader(filename);
 
     Console.WriteLine("----------Use pre-defined keywords----------");
 
-    OnlineStream s = kws.CreateStream();
+    var s = kws.CreateStream();
 
     Console.WriteLine(PortAudio.VersionInfo.versionText);
     PortAudio.Initialize();
@@ -54,7 +51,7 @@ static void Main(string[] args)
     for (int i = 0; i != PortAudio.DeviceCount; ++i)
     {
       Console.WriteLine($" Device {i}");
-      DeviceInfo deviceInfo = PortAudio.GetDeviceInfo(i);
+      var deviceInfo = PortAudio.GetDeviceInfo(i);
       Console.WriteLine($"   Name: {deviceInfo.name}");
       Console.WriteLine($"   Max input channels: {deviceInfo.maxInputChannels}");
       Console.WriteLine($"   Default sample rate: {deviceInfo.defaultSampleRate}");
@@ -66,12 +63,12 @@ static void Main(string[] args)
       Environment.Exit(1);
     }
 
-    DeviceInfo info = PortAudio.GetDeviceInfo(deviceIndex);
+    var info = PortAudio.GetDeviceInfo(deviceIndex);
 
     Console.WriteLine();
     Console.WriteLine($"Use default device {deviceIndex} ({info.name})");
 
-    StreamParameters param = new StreamParameters();
+    var param = new StreamParameters();
     param.device = deviceIndex;
     param.channelCount = 1;
     param.sampleFormat = SampleFormat.Float32;
@@ -79,21 +76,21 @@ static void Main(string[] args)
     param.hostApiSpecificStreamInfo = IntPtr.Zero;
 
     PortAudioSharp.Stream.Callback callback = (IntPtr input, IntPtr output,
-        UInt32 frameCount,
+        uint frameCount,
         ref StreamCallbackTimeInfo timeInfo,
         StreamCallbackFlags statusFlags,
         IntPtr userData
         ) =>
     {
-      float[] samples = new float[frameCount];
-      Marshal.Copy(input, samples, 0, (Int32)frameCount);
+      var samples = new float[frameCount];
+      Marshal.Copy(input, samples, 0, (int)frameCount);
 
       s.AcceptWaveform(config.FeatConfig.SampleRate, samples);
 
       return StreamCallbackResult.Continue;
     };
 
-    PortAudioSharp.Stream stream = new PortAudioSharp.Stream(inParams: param, outParams: null, sampleRate: config.FeatConfig.SampleRate,
+    var stream = new PortAudioSharp.Stream(inParams: param, outParams: null, sampleRate: config.FeatConfig.SampleRate,
         framesPerBuffer: 0,
         streamFlags: StreamFlags.ClipOff,
         callback: callback,
@@ -113,15 +110,13 @@ IntPtr userData
       }
 
       var result = kws.GetResult(s);
-      if (result.Keyword != "")
+      if (result.Keyword != string.Empty)
       {
         Console.WriteLine("Detected: {0}", result.Keyword);
       }
 
       Thread.Sleep(200); // ms
     }
-
-    PortAudio.Terminate();
   }
 }
 
diff --git a/dotnet-examples/keyword-spotting-from-microphone/keyword-spotting-from-microphone.csproj b/dotnet-examples/keyword-spotting-from-microphone/keyword-spotting-from-microphone.csproj
index b3afae784..12415b81b 100644
--- a/dotnet-examples/keyword-spotting-from-microphone/keyword-spotting-from-microphone.csproj
+++ b/dotnet-examples/keyword-spotting-from-microphone/keyword-spotting-from-microphone.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>keyword_spotting_from_microphone</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/offline-decode-files/Program.cs b/dotnet-examples/offline-decode-files/Program.cs
index d855da6f8..0d944e5a3 100644
--- a/dotnet-examples/offline-decode-files/Program.cs
+++ b/dotnet-examples/offline-decode-files/Program.cs
@@ -5,17 +5,14 @@
 // Please refer to
 // https://k2-fsa.github.io/sherpa/onnx/pretrained_models/index.html
 // to download non-streaming models
-using CommandLine.Text;
 using CommandLine;
+using CommandLine.Text;
 using SherpaOnnx;
-using System.Collections.Generic;
-using System;
 
 class OfflineDecodeFiles
 {
   class Options
   {
-
     [Option("sample-rate", Required = false, Default = 16000, HelpText = "Sample rate of the data used to train the model")]
     public int SampleRate { get; set; } = 16000;
 
@@ -23,58 +20,58 @@ class Options
     public int FeatureDim { get; set; } = 80;
 
     [Option(Required = false, HelpText = "Path to tokens.txt")]
-    public string Tokens { get; set; } = "";
+    public string Tokens { get; set; } = string.Empty;
 
     [Option(Required = false, Default = "", HelpText = "Path to transducer encoder.onnx. Used only for transducer models")]
-    public string Encoder { get; set; } = "";
+    public string Encoder { get; set; } = string.Empty;
 
     [Option(Required = false, Default = "", HelpText = "Path to transducer decoder.onnx. Used only for transducer models")]
-    public string Decoder { get; set; } = "";
+    public string Decoder { get; set; } = string.Empty;
 
     [Option(Required = false, Default = "", HelpText = "Path to transducer joiner.onnx. Used only for transducer models")]
-    public string Joiner { get; set; } = "";
+    public string Joiner { get; set; } = string.Empty;
 
     [Option("model-type", Required = false, Default = "", HelpText = "model type")]
-    public string ModelType { get; set; } = "";
+    public string ModelType { get; set; } = string.Empty;
 
     [Option("whisper-encoder", Required = false, Default = "", HelpText = "Path to whisper encoder.onnx. Used only for whisper models")]
-    public string WhisperEncoder { get; set; } = "";
+    public string WhisperEncoder { get; set; } = string.Empty;
 
     [Option("whisper-decoder", Required = false, Default = "", HelpText = "Path to whisper decoder.onnx. Used only for whisper models")]
-    public string WhisperDecoder { get; set; } = "";
+    public string WhisperDecoder { get; set; } = string.Empty;
 
     [Option("whisper-language", Required = false, Default = "", HelpText = "Language of the input file. Can be empty")]
-    public string WhisperLanguage { get; set; } = "";
+    public string WhisperLanguage { get; set; } = string.Empty;
 
     [Option("whisper-task", Required = false, Default = "transcribe", HelpText = "transcribe or translate")]
     public string WhisperTask { get; set; } = "transcribe";
 
     [Option("moonshine-preprocessor", Required = false, Default = "", HelpText = "Path to preprocess.onnx. Used only for Moonshine models")]
-    public string MoonshinePreprocessor { get; set; } = "";
+    public string MoonshinePreprocessor { get; set; } = string.Empty;
 
     [Option("moonshine-encoder", Required = false, Default = "", HelpText = "Path to encode.onnx. Used only for Moonshine models")]
-    public string MoonshineEncoder { get; set; } = "";
+    public string MoonshineEncoder { get; set; } = string.Empty;
 
     [Option("moonshine-uncached-decoder", Required = false, Default = "", HelpText = "Path to uncached_decode.onnx. Used only for Moonshine models")]
-    public string MoonshineUncachedDecoder { get; set; } = "";
+    public string MoonshineUncachedDecoder { get; set; } = string.Empty;
 
     [Option("moonshine-cached-decoder", Required = false, Default = "", HelpText = "Path to cached_decode.onnx. Used only for Moonshine models")]
-    public string MoonshineCachedDecoder { get; set; } = "";
+    public string MoonshineCachedDecoder { get; set; } = string.Empty;
 
     [Option("tdnn-model", Required = false, Default = "", HelpText = "Path to tdnn yesno model")]
-    public string TdnnModel { get; set; } = "";
+    public string TdnnModel { get; set; } = string.Empty;
 
     [Option(Required = false, HelpText = "Path to model.onnx. Used only for paraformer models")]
-    public string Paraformer { get; set; } = "";
+    public string Paraformer { get; set; } = string.Empty;
 
     [Option("nemo-ctc", Required = false, HelpText = "Path to model.onnx. Used only for NeMo CTC models")]
-    public string NeMoCtc { get; set; } = "";
+    public string NeMoCtc { get; set; } = string.Empty;
 
     [Option("telespeech-ctc", Required = false, HelpText = "Path to model.onnx. Used only for TeleSpeech CTC models")]
-    public string TeleSpeechCtc { get; set; } = "";
+    public string TeleSpeechCtc { get; set; } = string.Empty;
 
     [Option("sense-voice-model", Required = false, HelpText = "Path to model.onnx. Used only for SenseVoice CTC models")]
-    public string SenseVoiceModel { get; set; } = "";
+    public string SenseVoiceModel { get; set; } = string.Empty;
 
     [Option("sense-voice-use-itn", Required = false, HelpText = "1 to use inverse text normalization for sense voice.")]
     public int SenseVoiceUseItn { get; set; } = 1;
@@ -88,7 +85,7 @@ class Options
 
     [Option("rule-fsts", Required = false, Default = "",
             HelpText = "If not empty, path to rule fst for inverse text normalization")]
-    public string RuleFsts { get; set; } = "";
+    public string RuleFsts { get; set; } = string.Empty;
 
     [Option("max-active-paths", Required = false, Default = 4,
         HelpText = @"Used only when --decoding--method is modified_beam_search.
@@ -96,7 +93,7 @@ class Options
     public int MaxActivePaths { get; set; } = 4;
 
     [Option("hotwords-file", Required = false, Default = "", HelpText = "Path to hotwords.txt")]
-    public string HotwordsFile { get; set; } = "";
+    public string HotwordsFile { get; set; } = string.Empty;
 
     [Option("hotwords-score", Required = false, Default = 1.5F, HelpText = "hotwords score")]
     public float HotwordsScore { get; set; } = 1.5F;
@@ -117,7 +114,7 @@ static void Main(string[] args)
 
   private static void DisplayHelp<T>(ParserResult<T> result, IEnumerable<Error> errs)
   {
-    string usage = @"
+    var usage = @"
 # Zipformer
 
 dotnet run \
@@ -213,42 +210,42 @@ private static void Run(Options options)
 
     config.ModelConfig.Tokens = options.Tokens;
 
-    if (!String.IsNullOrEmpty(options.Encoder))
+    if (!string.IsNullOrEmpty(options.Encoder))
     {
       // this is a transducer model
       config.ModelConfig.Transducer.Encoder = options.Encoder;
       config.ModelConfig.Transducer.Decoder = options.Decoder;
       config.ModelConfig.Transducer.Joiner = options.Joiner;
     }
-    else if (!String.IsNullOrEmpty(options.Paraformer))
+    else if (!string.IsNullOrEmpty(options.Paraformer))
     {
       config.ModelConfig.Paraformer.Model = options.Paraformer;
     }
-    else if (!String.IsNullOrEmpty(options.NeMoCtc))
+    else if (!string.IsNullOrEmpty(options.NeMoCtc))
     {
       config.ModelConfig.NeMoCtc.Model = options.NeMoCtc;
     }
-    else if (!String.IsNullOrEmpty(options.TeleSpeechCtc))
+    else if (!string.IsNullOrEmpty(options.TeleSpeechCtc))
     {
       config.ModelConfig.TeleSpeechCtc = options.TeleSpeechCtc;
     }
-    else if (!String.IsNullOrEmpty(options.WhisperEncoder))
+    else if (!string.IsNullOrEmpty(options.WhisperEncoder))
     {
       config.ModelConfig.Whisper.Encoder = options.WhisperEncoder;
       config.ModelConfig.Whisper.Decoder = options.WhisperDecoder;
       config.ModelConfig.Whisper.Language = options.WhisperLanguage;
       config.ModelConfig.Whisper.Task = options.WhisperTask;
     }
-    else if (!String.IsNullOrEmpty(options.TdnnModel))
+    else if (!string.IsNullOrEmpty(options.TdnnModel))
     {
       config.ModelConfig.Tdnn.Model = options.TdnnModel;
     }
-    else if (!String.IsNullOrEmpty(options.SenseVoiceModel))
+    else if (!string.IsNullOrEmpty(options.SenseVoiceModel))
     {
       config.ModelConfig.SenseVoice.Model = options.SenseVoiceModel;
       config.ModelConfig.SenseVoice.UseInverseTextNormalization = options.SenseVoiceUseItn;
     }
-    else if (!String.IsNullOrEmpty(options.MoonshinePreprocessor))
+    else if (!string.IsNullOrEmpty(options.MoonshinePreprocessor))
     {
       config.ModelConfig.Moonshine.Preprocessor = options.MoonshinePreprocessor;
       config.ModelConfig.Moonshine.Encoder = options.MoonshineEncoder;
@@ -270,17 +267,17 @@ private static void Run(Options options)
 
     config.ModelConfig.Debug = 0;
 
-    OfflineRecognizer recognizer = new OfflineRecognizer(config);
+    var recognizer = new OfflineRecognizer(config);
 
-    string[] files = options.Files.ToArray();
+    var files = options.Files.ToArray();
 
     // We create a separate stream for each file
-    List<OfflineStream> streams = new List<OfflineStream>();
+    var streams = new List<OfflineStream>();
     streams.EnsureCapacity(files.Length);
 
     for (int i = 0; i != files.Length; ++i)
     {
-      OfflineStream s = recognizer.CreateStream();
+      var s = recognizer.CreateStream();
 
       WaveReader waveReader = new WaveReader(files[i]);
       s.AcceptWaveform(waveReader.SampleRate, waveReader.Samples);
@@ -299,7 +296,7 @@ private static void Run(Options options)
       Console.WriteLine("Tokens: [{0}]", string.Join(", ", r.Tokens));
       if (r.Timestamps != null && r.Timestamps.Length > 0) {
         Console.Write("Timestamps: [");
-        var sep = "";
+        var sep = string.Empty;
         for (int k = 0; k != r.Timestamps.Length; ++k)
         {
           Console.Write("{0}{1}", sep, r.Timestamps[k].ToString("0.00"));
diff --git a/dotnet-examples/offline-decode-files/offline-decode-files.csproj b/dotnet-examples/offline-decode-files/offline-decode-files.csproj
index ffdfb6ace..5b28d48b7 100644
--- a/dotnet-examples/offline-decode-files/offline-decode-files.csproj
+++ b/dotnet-examples/offline-decode-files/offline-decode-files.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>offline_decode_files</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/offline-punctuation/Program.cs b/dotnet-examples/offline-punctuation/Program.cs
index d299f8abc..6f85237b6 100644
--- a/dotnet-examples/offline-punctuation/Program.cs
+++ b/dotnet-examples/offline-punctuation/Program.cs
@@ -12,8 +12,6 @@
 // dotnet run
 
 using SherpaOnnx;
-using System.Collections.Generic;
-using System;
 
 class OfflinePunctuationDemo
 {
@@ -25,14 +23,14 @@ static void Main(string[] args)
     config.Model.NumThreads = 1;
     var punct = new OfflinePunctuation(config);
 
-    string[] textList = new string[] {
+    var textList = new string[] {
         "这是一个测试你好吗How are you我很好thank you are you ok谢谢你",
         "我们都是木头人不会说话不会动",
         "The African blogosphere is rapidly expanding bringing more voices online in the form of commentaries opinions analyses rants and poetry",
     };
 
     Console.WriteLine("---------");
-    foreach (string text in textList)
+    foreach (var text in textList)
     {
       string textWithPunct = punct.AddPunct(text);
       Console.WriteLine("Input text: {0}", text);
diff --git a/dotnet-examples/offline-punctuation/offline-punctuation.csproj b/dotnet-examples/offline-punctuation/offline-punctuation.csproj
index 2d94fcb38..0e3ee42a9 100644
--- a/dotnet-examples/offline-punctuation/offline-punctuation.csproj
+++ b/dotnet-examples/offline-punctuation/offline-punctuation.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>offline_punctuation</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/offline-speaker-diarization/Program.cs b/dotnet-examples/offline-speaker-diarization/Program.cs
index 45316fe75..4d8d91b0e 100644
--- a/dotnet-examples/offline-speaker-diarization/Program.cs
+++ b/dotnet-examples/offline-speaker-diarization/Program.cs
@@ -34,7 +34,6 @@ dotnet run
 */
 
 using SherpaOnnx;
-using System;
 
 class OfflineSpeakerDiarizationDemo
 {
@@ -54,7 +53,7 @@ static void Main(string[] args)
     var sd = new OfflineSpeakerDiarization(config);
 
     var testWaveFile = "./0-four-speakers-zh.wav";
-    WaveReader waveReader = new WaveReader(testWaveFile);
+    var waveReader = new WaveReader(testWaveFile);
     if (sd.SampleRate != waveReader.SampleRate)
     {
       Console.WriteLine($"Expected sample rate: {sd.SampleRate}. Given: {waveReader.SampleRate}");
@@ -65,19 +64,19 @@ static void Main(string[] args)
 
      // var segments = sd.Process(waveReader.Samples); // this one is also ok
 
-    var MyProgressCallback = (int numProcessedChunks, int numTotalChunks, IntPtr arg) =>
+    var progressCallback = (int numProcessedChunks, int numTotalChunks, IntPtr arg) =>
     {
-      float progress = 100.0F * numProcessedChunks / numTotalChunks;
-      Console.WriteLine("Progress {0}%", String.Format("{0:0.00}", progress));
+      var progress = 100.0F * numProcessedChunks / numTotalChunks;
+      Console.WriteLine("Progress {0}%", string.Format("{0:0.00}", progress));
       return 0;
     };
 
-    var callback = new OfflineSpeakerDiarizationProgressCallback(MyProgressCallback);
+    var callback = new OfflineSpeakerDiarizationProgressCallback(progressCallback);
     var segments = sd.ProcessWithCallback(waveReader.Samples, callback, IntPtr.Zero);
 
     foreach (var s in segments)
     {
-      Console.WriteLine("{0} -- {1} speaker_{2}", String.Format("{0:0.00}", s.Start), String.Format("{0:0.00}", s.End), s.Speaker);
+      Console.WriteLine("{0} -- {1} speaker_{2}", string.Format("{0:0.00}", s.Start), string.Format("{0:0.00}", s.End), s.Speaker);
     }
   }
 }
diff --git a/dotnet-examples/offline-speaker-diarization/offline-speaker-diarization.csproj b/dotnet-examples/offline-speaker-diarization/offline-speaker-diarization.csproj
index 3374dbca1..c7b15faa5 100644
--- a/dotnet-examples/offline-speaker-diarization/offline-speaker-diarization.csproj
+++ b/dotnet-examples/offline-speaker-diarization/offline-speaker-diarization.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>offline_speaker_diarization</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/offline-tts-play/Program.cs b/dotnet-examples/offline-tts-play/Program.cs
index a142c127e..65eb22bf4 100644
--- a/dotnet-examples/offline-tts-play/Program.cs
+++ b/dotnet-examples/offline-tts-play/Program.cs
@@ -10,15 +10,12 @@
 // Note that you need a speaker to run this file since it will play
 // the generated audio as it is generating.
 
-using CommandLine.Text;
 using CommandLine;
+using CommandLine.Text;
 using PortAudioSharp;
 using SherpaOnnx;
 using System.Collections.Concurrent;
-using System.Collections.Generic;
 using System.Runtime.InteropServices;
-using System.Threading;
-using System;
 
 class OfflineTtsPlayDemo
 {
@@ -26,13 +23,13 @@ class Options
   {
 
     [Option("tts-rule-fsts", Required = false, Default = "", HelpText = "path to rule.fst")]
-    public string RuleFsts { get; set; }
+    public string? RuleFsts { get; set; }
 
     [Option("vits-dict-dir", Required = false, Default = "", HelpText = "Path to the directory containing dict for jieba.")]
-    public string DictDir { get; set; }
+    public string? DictDir { get; set; }
 
     [Option("vits-data-dir", Required = false, Default = "", HelpText = "Path to the directory containing dict for espeak-ng.")]
-    public string DataDir { get; set; }
+    public string? DataDir { get; set; }
 
     [Option("vits-length-scale", Required = false, Default = 1, HelpText = "speech speed. Larger->Slower; Smaller->faster")]
     public float LengthScale { get; set; }
@@ -44,10 +41,10 @@ class Options
     public float NoiseScaleW { get; set; }
 
     [Option("vits-lexicon", Required = false, Default = "", HelpText = "Path to lexicon.txt")]
-    public string Lexicon { get; set; }
+    public string? Lexicon { get; set; }
 
     [Option("vits-tokens", Required = false, Default = "", HelpText = "Path to tokens.txt")]
-    public string Tokens { get; set; }
+    public string? Tokens { get; set; }
 
     [Option("tts-max-num-sentences", Required = false, Default = 1, HelpText = "Maximum number of sentences that we process at a time.")]
     public int MaxNumSentences { get; set; }
@@ -56,16 +53,16 @@ class Options
     public int Debug { get; set; }
 
     [Option("vits-model", Required = true, HelpText = "Path to VITS model")]
-    public string Model { get; set; }
+    public string? Model { get; set; }
 
     [Option("sid", Required = false, Default = 0, HelpText = "Speaker ID")]
     public int SpeakerId { get; set; }
 
     [Option("text", Required = true, HelpText = "Text to synthesize")]
-    public string Text { get; set; }
+    public string? Text { get; set; }
 
     [Option("output-filename", Required = true, Default = "./generated.wav", HelpText = "Path to save the generated audio")]
-    public string OutputFilename { get; set; }
+    public string? OutputFilename { get; set; }
   }
 
   static void Main(string[] args)
@@ -124,10 +121,9 @@ to download more models.
     Console.WriteLine(helpText);
   }
 
-
   private static void Run(Options options)
   {
-    OfflineTtsConfig config = new OfflineTtsConfig();
+    var config = new OfflineTtsConfig();
     config.Model.Vits.Model = options.Model;
     config.Model.Vits.Lexicon = options.Lexicon;
     config.Model.Vits.Tokens = options.Tokens;
@@ -142,10 +138,9 @@ private static void Run(Options options)
     config.RuleFsts = options.RuleFsts;
     config.MaxNumSentences = options.MaxNumSentences;
 
-    OfflineTts tts = new OfflineTts(config);
-    float speed = 1.0f / options.LengthScale;
-    int sid = options.SpeakerId;
-
+    var tts = new OfflineTts(config);
+    var speed = 1.0f / options.LengthScale;
+    var sid = options.SpeakerId;
 
     Console.WriteLine(PortAudio.VersionInfo.versionText);
     PortAudio.Initialize();
@@ -166,11 +161,11 @@ private static void Run(Options options)
       Environment.Exit(1);
     }
 
-    DeviceInfo info = PortAudio.GetDeviceInfo(deviceIndex);
+    var info = PortAudio.GetDeviceInfo(deviceIndex);
     Console.WriteLine();
     Console.WriteLine($"Use output default device {deviceIndex} ({info.name})");
 
-    StreamParameters param = new StreamParameters();
+    var param = new StreamParameters();
     param.device = deviceIndex;
     param.channelCount = 1;
     param.sampleFormat = SampleFormat.Float32;
@@ -178,7 +173,7 @@ private static void Run(Options options)
     param.hostApiSpecificStreamInfo = IntPtr.Zero;
 
     // https://learn.microsoft.com/en-us/dotnet/standard/collections/thread-safe/blockingcollection-overview
-    BlockingCollection<float[]> dataItems = new BlockingCollection<float[]>();
+    var dataItems = new BlockingCollection<float[]>();
 
     var MyCallback = (IntPtr samples, int n) =>
     {
@@ -193,9 +188,9 @@ private static void Run(Options options)
       return 1;
     };
 
-    bool playFinished = false;
+    var playFinished = false;
 
-    float[] lastSampleArray = null;
+    float[]? lastSampleArray = null;
     int lastIndex = 0; // not played
 
     PortAudioSharp.Stream.Callback playCallback = (IntPtr input, IntPtr output,
@@ -270,10 +265,10 @@ IntPtr userData
 
     stream.Start();
 
-    OfflineTtsCallback callback = new OfflineTtsCallback(MyCallback);
+    var callback = new OfflineTtsCallback(MyCallback);
 
-    OfflineTtsGeneratedAudio audio = tts.GenerateWithCallback(options.Text, speed, sid, callback);
-    bool ok = audio.SaveToWaveFile(options.OutputFilename);
+    var audio = tts.GenerateWithCallback(options.Text, speed, sid, callback);
+    var ok = audio.SaveToWaveFile(options.OutputFilename);
 
     if (ok)
     {
diff --git a/dotnet-examples/offline-tts-play/offline-tts-play.csproj b/dotnet-examples/offline-tts-play/offline-tts-play.csproj
index d28ae62c8..b777bcafe 100644
--- a/dotnet-examples/offline-tts-play/offline-tts-play.csproj
+++ b/dotnet-examples/offline-tts-play/offline-tts-play.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>offline_tts_play</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/offline-tts/Program.cs b/dotnet-examples/offline-tts/Program.cs
index 6216095f4..f434ebf19 100644
--- a/dotnet-examples/offline-tts/Program.cs
+++ b/dotnet-examples/offline-tts/Program.cs
@@ -6,28 +6,25 @@
 // and
 // https://github.com/k2-fsa/sherpa-onnx/releases/tag/tts-models
 // to download pre-trained models
-using CommandLine.Text;
 using CommandLine;
+using CommandLine.Text;
 using SherpaOnnx;
-using System.Collections.Generic;
-using System;
 
 class OfflineTtsDemo
 {
   class Options
   {
-
     [Option("tts-rule-fsts", Required = false, Default = "", HelpText = "path to rule.fst")]
-    public string RuleFsts { get; set; } = "";
+    public string RuleFsts { get; set; } = string.Empty;
 
     [Option("tts-rule-fars", Required = false, Default = "", HelpText = "path to rule.far")]
-    public string RuleFars { get; set; } = "";
+    public string RuleFars { get; set; } = string.Empty;
 
     [Option("vits-dict-dir", Required = false, Default = "", HelpText = "Path to the directory containing dict for jieba.")]
-    public string DictDir { get; set; } = "";
+    public string DictDir { get; set; } = string.Empty;
 
     [Option("vits-data-dir", Required = false, Default = "", HelpText = "Path to the directory containing dict for espeak-ng.")]
-    public string DataDir { get; set; } = "";
+    public string DataDir { get; set; } = string.Empty;
 
     [Option("vits-length-scale", Required = false, Default = 1, HelpText = "speech speed. Larger->Slower; Smaller->faster")]
     public float LengthScale { get; set; } = 1;
@@ -39,10 +36,10 @@ class Options
     public float NoiseScaleW { get; set; } = 0.8F;
 
     [Option("vits-lexicon", Required = false, Default = "", HelpText = "Path to lexicon.txt")]
-    public string Lexicon { get; set; } = "";
+    public string Lexicon { get; set; } = string.Empty;
 
     [Option("vits-tokens", Required = false, Default = "", HelpText = "Path to tokens.txt")]
-    public string Tokens { get; set; } = "";
+    public string Tokens { get; set; } = string.Empty;
 
     [Option("tts-max-num-sentences", Required = false, Default = 1, HelpText = "Maximum number of sentences that we process at a time.")]
     public int MaxNumSentences { get; set; } = 1;
@@ -51,13 +48,13 @@ class Options
     public int Debug { get; set; } = 0;
 
     [Option("vits-model", Required = true, HelpText = "Path to VITS model")]
-    public string Model { get; set; } = "";
+    public string Model { get; set; } = string.Empty;
 
     [Option("sid", Required = false, Default = 0, HelpText = "Speaker ID")]
     public int SpeakerId { get; set; } = 0;
 
     [Option("text", Required = true, HelpText = "Text to synthesize")]
-    public string Text { get; set; } = "";
+    public string Text { get; set; } = string.Empty;
 
     [Option("output-filename", Required = true, Default = "./generated.wav", HelpText = "Path to save the generated audio")]
     public string OutputFilename { get; set; } = "./generated.wav";
@@ -65,7 +62,7 @@ class Options
 
   static void Main(string[] args)
   {
-    var parser = new CommandLine.Parser(with => with.HelpWriter = null);
+    var parser = new Parser(with => with.HelpWriter = null);
     var parserResult = parser.ParseArguments<Options>(args);
 
     parserResult
@@ -75,7 +72,7 @@ static void Main(string[] args)
 
   private static void DisplayHelp<T>(ParserResult<T> result, IEnumerable<Error> errs)
   {
-    string usage = @"
+    var usage = @"
 # vits-aishell3
 
 curl -SL -O https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-icefall-zh-aishell3.tar.bz2
@@ -122,7 +119,7 @@ to download more models.
 
   private static void Run(Options options)
   {
-    OfflineTtsConfig config = new OfflineTtsConfig();
+    var config = new OfflineTtsConfig();
     config.Model.Vits.Model = options.Model;
     config.Model.Vits.Lexicon = options.Lexicon;
     config.Model.Vits.Tokens = options.Tokens;
@@ -138,11 +135,11 @@ private static void Run(Options options)
     config.RuleFars = options.RuleFars;
     config.MaxNumSentences = options.MaxNumSentences;
 
-    OfflineTts tts = new OfflineTts(config);
-    float speed = 1.0f / options.LengthScale;
-    int sid = options.SpeakerId;
-    OfflineTtsGeneratedAudio audio = tts.Generate(options.Text, speed, sid);
-    bool ok = audio.SaveToWaveFile(options.OutputFilename);
+    var tts = new OfflineTts(config);
+    var speed = 1.0f / options.LengthScale;
+    var sid = options.SpeakerId;
+    var audio = tts.Generate(options.Text, speed, sid);
+    var ok = audio.SaveToWaveFile(options.OutputFilename);
 
     if (ok)
     {
diff --git a/dotnet-examples/offline-tts/offline-tts.csproj b/dotnet-examples/offline-tts/offline-tts.csproj
index 48548fc4c..20b048f19 100644
--- a/dotnet-examples/offline-tts/offline-tts.csproj
+++ b/dotnet-examples/offline-tts/offline-tts.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>offline_tts</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/online-decode-files/Program.cs b/dotnet-examples/online-decode-files/Program.cs
index ad53624de..a1f01be57 100644
--- a/dotnet-examples/online-decode-files/Program.cs
+++ b/dotnet-examples/online-decode-files/Program.cs
@@ -6,40 +6,37 @@
 // https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-transducer/zipformer-transducer-models.html
 // to download streaming models
 
-using CommandLine.Text;
 using CommandLine;
+using CommandLine.Text;
 using SherpaOnnx;
-using System.Collections.Generic;
-using System.Linq;
-using System;
 
 class OnlineDecodeFiles
 {
   class Options
   {
     [Option(Required = true, HelpText = "Path to tokens.txt")]
-    public string Tokens { get; set; } = "";
+    public string Tokens { get; set; } = string.Empty;
 
     [Option(Required = false, Default = "cpu", HelpText = "Provider, e.g., cpu, coreml")]
-    public string Provider { get; set; } = "";
+    public string Provider { get; set; } = string.Empty;
 
     [Option(Required = false, HelpText = "Path to transducer encoder.onnx")]
-    public string Encoder { get; set; } = "";
+    public string Encoder { get; set; } = string.Empty;
 
     [Option(Required = false, HelpText = "Path to transducer decoder.onnx")]
-    public string Decoder { get; set; } = "";
+    public string Decoder { get; set; } = string.Empty;
 
     [Option(Required = false, HelpText = "Path to transducer joiner.onnx")]
-    public string Joiner { get; set; } = "";
+    public string Joiner { get; set; } = string.Empty;
 
     [Option("paraformer-encoder", Required = false, HelpText = "Path to paraformer encoder.onnx")]
-    public string ParaformerEncoder { get; set; } = "";
+    public string ParaformerEncoder { get; set; } = string.Empty;
 
     [Option("paraformer-decoder", Required = false, HelpText = "Path to paraformer decoder.onnx")]
-    public string ParaformerDecoder { get; set; } = "";
+    public string ParaformerDecoder { get; set; } = string.Empty;
 
     [Option("zipformer2-ctc", Required = false, HelpText = "Path to zipformer2 CTC onnx model")]
-    public string Zipformer2Ctc { get; set; } = "";
+    public string Zipformer2Ctc { get; set; } = string.Empty;
 
     [Option("num-threads", Required = false, Default = 1, HelpText = "Number of threads for computation")]
     public int NumThreads { get; set; } = 1;
@@ -80,15 +77,14 @@ larger than this value after something that is not blank has been decoded. Used
     public float Rule3MinUtteranceLength { get; set; } = 20.0F;
 
     [Option("hotwords-file", Required = false, Default = "", HelpText = "Path to hotwords.txt")]
-    public string HotwordsFile { get; set; } = "";
+    public string HotwordsFile { get; set; } = string.Empty;
 
     [Option("hotwords-score", Required = false, Default = 1.5F, HelpText = "hotwords score")]
     public float HotwordsScore { get; set; } = 1.5F;
 
     [Option("rule-fsts", Required = false, Default = "",
             HelpText = "If not empty, path to rule fst for inverse text normalization")]
-    public string RuleFsts { get; set; } = "";
-
+    public string RuleFsts { get; set; } = string.Empty;
 
     [Option("files", Required = true, HelpText = "Audio files for decoding")]
     public IEnumerable<string> Files { get; set; } = new string[] {};
@@ -162,7 +158,7 @@ to download pre-trained streaming models.
 
   private static void Run(Options options)
   {
-    OnlineRecognizerConfig config = new OnlineRecognizerConfig();
+    var config = new OnlineRecognizerConfig();
     config.FeatConfig.SampleRate = options.SampleRate;
 
     // All models from icefall using feature dim 80.
@@ -194,22 +190,22 @@ private static void Run(Options options)
     config.HotwordsScore = options.HotwordsScore;
     config.RuleFsts = options.RuleFsts;
 
-    OnlineRecognizer recognizer = new OnlineRecognizer(config);
+    var recognizer = new OnlineRecognizer(config);
 
-    string[] files = options.Files.ToArray();
+    var files = options.Files.ToArray();
 
     // We create a separate stream for each file
-    List<OnlineStream> streams = new List<OnlineStream>();
+    var streams = new List<OnlineStream>();
     streams.EnsureCapacity(files.Length);
 
     for (int i = 0; i != files.Length; ++i)
     {
-      OnlineStream s = recognizer.CreateStream();
+      var s = recognizer.CreateStream();
 
-      WaveReader waveReader = new WaveReader(files[i]);
+      var waveReader = new WaveReader(files[i]);
       s.AcceptWaveform(waveReader.SampleRate, waveReader.Samples);
 
-      float[] tailPadding = new float[(int)(waveReader.SampleRate * 0.3)];
+      var tailPadding = new float[(int)(waveReader.SampleRate * 0.3)];
       s.AcceptWaveform(waveReader.SampleRate, tailPadding);
       s.InputFinished();
 
@@ -230,7 +226,7 @@ private static void Run(Options options)
     // display results
     for (int i = 0; i != files.Length; ++i)
     {
-      OnlineRecognizerResult r = recognizer.GetResult(streams[i]);
+      var r = recognizer.GetResult(streams[i]);
       var text = r.Text;
       var tokens = r.Tokens;
       Console.WriteLine("--------------------");
@@ -238,7 +234,7 @@ private static void Run(Options options)
       Console.WriteLine("text: {0}", text);
       Console.WriteLine("tokens: [{0}]", string.Join(", ", tokens));
       Console.Write("timestamps: [");
-      r.Timestamps.ToList().ForEach(i => Console.Write(String.Format("{0:0.00}", i) + ", "));
+      r.Timestamps.ToList().ForEach(i => Console.Write(string.Format("{0:0.00}", i) + ", "));
       Console.WriteLine("]");
     }
     Console.WriteLine("--------------------");
diff --git a/dotnet-examples/online-decode-files/online-decode-files.csproj b/dotnet-examples/online-decode-files/online-decode-files.csproj
index 0ff581102..f1cc3baa7 100644
--- a/dotnet-examples/online-decode-files/online-decode-files.csproj
+++ b/dotnet-examples/online-decode-files/online-decode-files.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>online_decode_files</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/sherpa-onnx.sln b/dotnet-examples/sherpa-onnx.sln
index 0bff03f5c..1ebcdf464 100644
--- a/dotnet-examples/sherpa-onnx.sln
+++ b/dotnet-examples/sherpa-onnx.sln
@@ -29,9 +29,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "keyword-spotting-from-files
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "keyword-spotting-from-microphone", "keyword-spotting-from-microphone\keyword-spotting-from-microphone.csproj", "{AEE0ED2B-C86F-4952-863C-EAD3219CB4EC}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "TTS", "TTS\TTS.csproj", "{DACE4A18-4FC8-4437-92BF-5A90BA81286C}"
-EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "offline-speaker-diarization", "offline-speaker-diarization\offline-speaker-diarization.csproj", "{D3A1FF28-A77D-429D-AEAC-2BA77CA682BC}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "offline-speaker-diarization", "offline-speaker-diarization\offline-speaker-diarization.csproj", "{D3A1FF28-A77D-429D-AEAC-2BA77CA682BC}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -91,10 +89,6 @@ Global
 		{AEE0ED2B-C86F-4952-863C-EAD3219CB4EC}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{AEE0ED2B-C86F-4952-863C-EAD3219CB4EC}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{AEE0ED2B-C86F-4952-863C-EAD3219CB4EC}.Release|Any CPU.Build.0 = Release|Any CPU
-		{DACE4A18-4FC8-4437-92BF-5A90BA81286C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{DACE4A18-4FC8-4437-92BF-5A90BA81286C}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{DACE4A18-4FC8-4437-92BF-5A90BA81286C}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{DACE4A18-4FC8-4437-92BF-5A90BA81286C}.Release|Any CPU.Build.0 = Release|Any CPU
 		{D3A1FF28-A77D-429D-AEAC-2BA77CA682BC}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{D3A1FF28-A77D-429D-AEAC-2BA77CA682BC}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{D3A1FF28-A77D-429D-AEAC-2BA77CA682BC}.Release|Any CPU.ActiveCfg = Release|Any CPU
diff --git a/dotnet-examples/speaker-identification/Program.cs b/dotnet-examples/speaker-identification/Program.cs
index aef53e851..20ac70390 100644
--- a/dotnet-examples/speaker-identification/Program.cs
+++ b/dotnet-examples/speaker-identification/Program.cs
@@ -16,20 +16,18 @@
 // dotnet run
 
 using SherpaOnnx;
-using System.Collections.Generic;
-using System;
 
 class SpeakerIdentificationDemo
 {
-  public static float[] ComputeEmbedding(SpeakerEmbeddingExtractor extractor, String filename)
+  public static float[] ComputeEmbedding(SpeakerEmbeddingExtractor extractor, string filename)
   {
-    WaveReader reader = new WaveReader(filename);
+    var reader = new WaveReader(filename);
 
-    OnlineStream stream = extractor.CreateStream();
+    var stream = extractor.CreateStream();
     stream.AcceptWaveform(reader.SampleRate, reader.Samples);
     stream.InputFinished();
 
-    float[] embedding = extractor.Compute(stream);
+    var embedding = extractor.Compute(stream);
 
     return embedding;
   }
@@ -43,25 +41,25 @@ static void Main(string[] args)
 
     var manager = new SpeakerEmbeddingManager(extractor.Dim);
 
-    string[] spk1Files =
+    var spk1Files =
         new string[] {
           "./sr-data/enroll/fangjun-sr-1.wav",
           "./sr-data/enroll/fangjun-sr-2.wav",
           "./sr-data/enroll/fangjun-sr-3.wav",
         };
-    float[][] spk1Vec = new float[spk1Files.Length][];
+    var spk1Vec = new float[spk1Files.Length][];
 
     for (int i = 0; i < spk1Files.Length; ++i)
     {
       spk1Vec[i] = ComputeEmbedding(extractor, spk1Files[i]);
     }
 
-    string[] spk2Files =
+    var spk2Files =
         new string[] {
           "./sr-data/enroll/leijun-sr-1.wav", "./sr-data/enroll/leijun-sr-2.wav",
         };
 
-    float[][] spk2Vec = new float[spk2Files.Length][];
+    var spk2Vec = new float[spk2Files.Length][];
 
     for (int i = 0; i < spk2Files.Length; ++i)
     {
@@ -100,14 +98,14 @@ static void Main(string[] args)
 
     Console.WriteLine("---All speakers---");
 
-    string[] allSpeakers = manager.GetAllSpeakers();
+    var allSpeakers = manager.GetAllSpeakers();
     foreach (var s in allSpeakers)
     {
       Console.WriteLine(s);
     }
     Console.WriteLine("------------");
 
-    string[] testFiles =
+    var testFiles =
         new string[] {
           "./sr-data/test/fangjun-test-sr-1.wav",
           "./sr-data/test/leijun-test-sr-1.wav",
@@ -117,9 +115,9 @@ static void Main(string[] args)
     float threshold = 0.6f;
     foreach (var file in testFiles)
     {
-      float[] embedding = ComputeEmbedding(extractor, file);
+      var embedding = ComputeEmbedding(extractor, file);
 
-      String name = manager.Search(embedding, threshold);
+      var name = manager.Search(embedding, threshold);
       if (name == "")
       {
         name = "<Unknown>";
diff --git a/dotnet-examples/speaker-identification/speaker-identification.csproj b/dotnet-examples/speaker-identification/speaker-identification.csproj
index 7c857fa54..45a42f49e 100644
--- a/dotnet-examples/speaker-identification/speaker-identification.csproj
+++ b/dotnet-examples/speaker-identification/speaker-identification.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>speaker_identification</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/speech-recognition-from-microphone/Program.cs b/dotnet-examples/speech-recognition-from-microphone/Program.cs
index 586e3b162..aa0e7803f 100644
--- a/dotnet-examples/speech-recognition-from-microphone/Program.cs
+++ b/dotnet-examples/speech-recognition-from-microphone/Program.cs
@@ -6,47 +6,43 @@
 // https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-transducer/zipformer-transducer-models.html
 // to download streaming models
 
-using CommandLine.Text;
 using CommandLine;
+using CommandLine.Text;
 using PortAudioSharp;
-using System.Threading;
 using SherpaOnnx;
-using System.Collections.Generic;
 using System.Runtime.InteropServices;
-using System;
-
 
 class SpeechRecognitionFromMicrophone
 {
   class Options
   {
     [Option(Required = true, HelpText = "Path to tokens.txt")]
-    public string Tokens { get; set; }
+    public string? Tokens { get; set; }
 
     [Option(Required = false, Default = "cpu", HelpText = "Provider, e.g., cpu, coreml")]
-    public string Provider { get; set; }
+    public string? Provider { get; set; }
 
     [Option(Required = false, HelpText = "Path to transducer encoder.onnx")]
-    public string Encoder { get; set; }
+    public string? Encoder { get; set; }
 
     [Option(Required = false, HelpText = "Path to transducer decoder.onnx")]
-    public string Decoder { get; set; }
+    public string? Decoder { get; set; }
 
     [Option(Required = false, HelpText = "Path to transducer joiner.onnx")]
-    public string Joiner { get; set; }
+    public string? Joiner { get; set; }
 
     [Option("paraformer-encoder", Required = false, HelpText = "Path to paraformer encoder.onnx")]
-    public string ParaformerEncoder { get; set; }
+    public string? ParaformerEncoder { get; set; }
 
     [Option("paraformer-decoder", Required = false, HelpText = "Path to paraformer decoder.onnx")]
-    public string ParaformerDecoder { get; set; }
+    public string? ParaformerDecoder { get; set; }
 
     [Option("num-threads", Required = false, Default = 1, HelpText = "Number of threads for computation")]
     public int NumThreads { get; set; }
 
     [Option("decoding-method", Required = false, Default = "greedy_search",
             HelpText = "Valid decoding methods are: greedy_search, modified_beam_search")]
-    public string DecodingMethod { get; set; }
+    public string? DecodingMethod { get; set; }
 
     [Option(Required = false, Default = false, HelpText = "True to show model info during loading")]
     public bool Debug { get; set; }
@@ -126,7 +122,7 @@ to download pre-trained streaming models.
 
   private static void Run(Options options)
   {
-    OnlineRecognizerConfig config = new OnlineRecognizerConfig();
+    var config = new OnlineRecognizerConfig();
     config.FeatConfig.SampleRate = options.SampleRate;
 
     // All models from icefall using feature dim 80.
@@ -153,9 +149,9 @@ private static void Run(Options options)
     config.Rule2MinTrailingSilence = options.Rule2MinTrailingSilence;
     config.Rule3MinUtteranceLength = options.Rule3MinUtteranceLength;
 
-    OnlineRecognizer recognizer = new OnlineRecognizer(config);
+    var recognizer = new OnlineRecognizer(config);
 
-    OnlineStream s = recognizer.CreateStream();
+    var s = recognizer.CreateStream();
 
     Console.WriteLine(PortAudio.VersionInfo.versionText);
     PortAudio.Initialize();
@@ -176,12 +172,12 @@ private static void Run(Options options)
       Environment.Exit(1);
     }
 
-    DeviceInfo info = PortAudio.GetDeviceInfo(deviceIndex);
+    var info = PortAudio.GetDeviceInfo(deviceIndex);
 
     Console.WriteLine();
     Console.WriteLine($"Use default device {deviceIndex} ({info.name})");
 
-    StreamParameters param = new StreamParameters();
+    var param = new StreamParameters();
     param.device = deviceIndex;
     param.channelCount = 1;
     param.sampleFormat = SampleFormat.Float32;
@@ -189,14 +185,14 @@ private static void Run(Options options)
     param.hostApiSpecificStreamInfo = IntPtr.Zero;
 
     PortAudioSharp.Stream.Callback callback = (IntPtr input, IntPtr output,
-        UInt32 frameCount,
+        uint frameCount,
         ref StreamCallbackTimeInfo timeInfo,
         StreamCallbackFlags statusFlags,
         IntPtr userData
         ) =>
     {
-      float[] samples = new float[frameCount];
-      Marshal.Copy(input, samples, 0, (Int32)frameCount);
+      var samples = new float[frameCount];
+      Marshal.Copy(input, samples, 0, (int)frameCount);
 
       s.AcceptWaveform(options.SampleRate, samples);
 
@@ -215,7 +211,7 @@ IntPtr userData
 
     stream.Start();
 
-    String lastText = "";
+    var lastText = string.Empty;
     int segmentIndex = 0;
 
     while (true)
@@ -245,9 +241,5 @@ IntPtr userData
 
       Thread.Sleep(200); // ms
     }
-
-    PortAudio.Terminate();
-
-
   }
 }
diff --git a/dotnet-examples/speech-recognition-from-microphone/speech-recognition-from-microphone.csproj b/dotnet-examples/speech-recognition-from-microphone/speech-recognition-from-microphone.csproj
index 901c8a158..72b7b6c91 100644
--- a/dotnet-examples/speech-recognition-from-microphone/speech-recognition-from-microphone.csproj
+++ b/dotnet-examples/speech-recognition-from-microphone/speech-recognition-from-microphone.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>speech_recognition_from_microphone</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/spoken-language-identification/Program.cs b/dotnet-examples/spoken-language-identification/Program.cs
index 05a785d7c..d2f210e85 100644
--- a/dotnet-examples/spoken-language-identification/Program.cs
+++ b/dotnet-examples/spoken-language-identification/Program.cs
@@ -15,12 +15,9 @@
 // dotnet run
 
 using SherpaOnnx;
-using System.Collections.Generic;
-using System;
 
 class SpokenLanguageIdentificationDemo
 {
-
   static void Main(string[] args)
   {
     var config = new SpokenLanguageIdentificationConfig();
@@ -30,7 +27,7 @@ static void Main(string[] args)
     var slid = new SpokenLanguageIdentification(config);
     var filename = "./sherpa-onnx-whisper-tiny/test_wavs/0.wav";
 
-    WaveReader waveReader = new WaveReader(filename);
+    var waveReader = new WaveReader(filename);
 
     var s = slid.CreateStream();
     s.AcceptWaveform(waveReader.SampleRate, waveReader.Samples);
diff --git a/dotnet-examples/spoken-language-identification/spoken-language-identification.csproj b/dotnet-examples/spoken-language-identification/spoken-language-identification.csproj
index b8b431a48..e424b2d57 100644
--- a/dotnet-examples/spoken-language-identification/spoken-language-identification.csproj
+++ b/dotnet-examples/spoken-language-identification/spoken-language-identification.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>spoken_language_identification</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/streaming-hlg-decoding/Program.cs b/dotnet-examples/streaming-hlg-decoding/Program.cs
index 6ac7c8c94..e522b8164 100644
--- a/dotnet-examples/streaming-hlg-decoding/Program.cs
+++ b/dotnet-examples/streaming-hlg-decoding/Program.cs
@@ -13,12 +13,9 @@
 // dotnet run
 
 using SherpaOnnx;
-using System.Collections.Generic;
-using System;
 
 class StreamingHlgDecodingDemo
 {
-
   static void Main(string[] args)
   {
     var config = new OnlineRecognizerConfig();
@@ -32,15 +29,15 @@ static void Main(string[] args)
     config.ModelConfig.Debug = 0;
     config.CtcFstDecoderConfig.Graph = "./sherpa-onnx-streaming-zipformer-ctc-small-2024-03-18/HLG.fst";
 
-    OnlineRecognizer recognizer = new OnlineRecognizer(config);
+    var recognizer = new OnlineRecognizer(config);
 
     var filename = "./sherpa-onnx-streaming-zipformer-ctc-small-2024-03-18/test_wavs/8k.wav";
 
-    WaveReader waveReader = new WaveReader(filename);
-    OnlineStream s = recognizer.CreateStream();
+    var waveReader = new WaveReader(filename);
+    var s = recognizer.CreateStream();
     s.AcceptWaveform(waveReader.SampleRate, waveReader.Samples);
 
-    float[] tailPadding = new float[(int)(waveReader.SampleRate * 0.3)];
+    var tailPadding = new float[(int)(waveReader.SampleRate * 0.3)];
     s.AcceptWaveform(waveReader.SampleRate, tailPadding);
     s.InputFinished();
 
@@ -49,7 +46,7 @@ static void Main(string[] args)
       recognizer.Decode(s);
     }
 
-    OnlineRecognizerResult r = recognizer.GetResult(s);
+    var r = recognizer.GetResult(s);
     var text = r.Text;
     var tokens = r.Tokens;
     Console.WriteLine("--------------------");
@@ -57,10 +54,8 @@ static void Main(string[] args)
     Console.WriteLine("text: {0}", text);
     Console.WriteLine("tokens: [{0}]", string.Join(", ", tokens));
     Console.Write("timestamps: [");
-    r.Timestamps.ToList().ForEach(i => Console.Write(String.Format("{0:0.00}", i) + ", "));
+    r.Timestamps.ToList().ForEach(i => Console.Write(string.Format("{0:0.00}", i) + ", "));
     Console.WriteLine("]");
     Console.WriteLine("--------------------");
   }
 }
-
-
diff --git a/dotnet-examples/streaming-hlg-decoding/streaming-hlg-decoding.csproj b/dotnet-examples/streaming-hlg-decoding/streaming-hlg-decoding.csproj
index 66e0401f1..6ed8fc699 100644
--- a/dotnet-examples/streaming-hlg-decoding/streaming-hlg-decoding.csproj
+++ b/dotnet-examples/streaming-hlg-decoding/streaming-hlg-decoding.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>streaming_hlg_decoding</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/dotnet-examples/vad-non-streaming-asr-paraformer/Program.cs b/dotnet-examples/vad-non-streaming-asr-paraformer/Program.cs
index abc080b88..e8dfbe6fa 100644
--- a/dotnet-examples/vad-non-streaming-asr-paraformer/Program.cs
+++ b/dotnet-examples/vad-non-streaming-asr-paraformer/Program.cs
@@ -3,8 +3,6 @@
 // This file shows how to use a silero_vad model with a non-streaming Paraformer
 // for speech recognition.
 using SherpaOnnx;
-using System.Collections.Generic;
-using System;
 
 class VadNonStreamingAsrParaformer
 {
@@ -12,45 +10,49 @@ static void Main(string[] args)
   {
     // please download model files from
     // https://github.com/k2-fsa/sherpa-onnx/releases/tag/asr-models
-    OfflineRecognizerConfig config = new OfflineRecognizerConfig();
+    var config = new OfflineRecognizerConfig();
     config.ModelConfig.Paraformer.Model = "./sherpa-onnx-paraformer-zh-2023-09-14/model.int8.onnx";
     config.ModelConfig.Tokens = "./sherpa-onnx-paraformer-zh-2023-09-14/tokens.txt";
     config.ModelConfig.Debug = 0;
-    OfflineRecognizer recognizer = new OfflineRecognizer(config);
+    var recognizer = new OfflineRecognizer(config);
 
-    VadModelConfig vadModelConfig = new VadModelConfig();
+    var vadModelConfig = new VadModelConfig();
     vadModelConfig.SileroVad.Model = "./silero_vad.onnx";
     vadModelConfig.Debug = 0;
 
-    VoiceActivityDetector vad = new VoiceActivityDetector(vadModelConfig, 60);
+    var vad = new VoiceActivityDetector(vadModelConfig, 60);
 
-    string testWaveFilename = "./lei-jun-test.wav";
-    WaveReader reader = new WaveReader(testWaveFilename);
+    var testWaveFilename = "./lei-jun-test.wav";
+    var reader = new WaveReader(testWaveFilename);
 
     int numSamples = reader.Samples.Length;
     int windowSize = vadModelConfig.SileroVad.WindowSize;
     int sampleRate = vadModelConfig.SampleRate;
     int numIter = numSamples / windowSize;
 
-    for (int i = 0; i != numIter; ++i) {
+    for (int i = 0; i != numIter; ++i)
+    {
       int start = i * windowSize;
-      float[] samples = new float[windowSize];
+      var samples = new float[windowSize];
       Array.Copy(reader.Samples, start, samples, 0, windowSize);
       vad.AcceptWaveform(samples);
-      if (vad.IsSpeechDetected()) {
-        while (!vad.IsEmpty()) {
+      if (vad.IsSpeechDetected())
+      {
+        while (!vad.IsEmpty())
+        {
           SpeechSegment segment = vad.Front();
-          float startTime = segment.Start / (float)sampleRate;
-          float duration = segment.Samples.Length / (float)sampleRate;
+          var startTime = segment.Start / (float)sampleRate;
+          var duration = segment.Samples.Length / (float)sampleRate;
 
           OfflineStream stream = recognizer.CreateStream();
           stream.AcceptWaveform(sampleRate, segment.Samples);
           recognizer.Decode(stream);
-          String text = stream.Result.Text;
+          var text = stream.Result.Text;
 
-          if (!String.IsNullOrEmpty(text)) {
-            Console.WriteLine("{0}--{1}: {2}", String.Format("{0:0.00}", startTime),
-                String.Format("{0:0.00}", startTime+duration), text);
+          if (!string.IsNullOrEmpty(text))
+          {
+            Console.WriteLine("{0}--{1}: {2}", string.Format("{0:0.00}", startTime),
+                string.Format("{0:0.00}", startTime + duration), text);
           }
 
           vad.Pop();
@@ -60,19 +62,21 @@ static void Main(string[] args)
 
     vad.Flush();
 
-    while (!vad.IsEmpty()) {
-      SpeechSegment segment = vad.Front();
+    while (!vad.IsEmpty())
+    {
+      var segment = vad.Front();
       float startTime = segment.Start / (float)sampleRate;
       float duration = segment.Samples.Length / (float)sampleRate;
 
-      OfflineStream stream = recognizer.CreateStream();
+      var stream = recognizer.CreateStream();
       stream.AcceptWaveform(sampleRate, segment.Samples);
       recognizer.Decode(stream);
-      String text = stream.Result.Text;
+      var text = stream.Result.Text;
 
-      if (!String.IsNullOrEmpty(text)) {
-        Console.WriteLine("{0}--{1}: {2}", String.Format("{0:0.00}", startTime),
-            String.Format("{0:0.00}", startTime+duration), text);
+      if (!string.IsNullOrEmpty(text))
+      {
+        Console.WriteLine("{0}--{1}: {2}", string.Format("{0:0.00}", startTime),
+            string.Format("{0:0.00}", startTime + duration), text);
       }
 
       vad.Pop();
diff --git a/dotnet-examples/vad-non-streaming-asr-paraformer/vad-non-streaming-asr-paraformer.csproj b/dotnet-examples/vad-non-streaming-asr-paraformer/vad-non-streaming-asr-paraformer.csproj
index a5c5f1022..1736869a8 100644
--- a/dotnet-examples/vad-non-streaming-asr-paraformer/vad-non-streaming-asr-paraformer.csproj
+++ b/dotnet-examples/vad-non-streaming-asr-paraformer/vad-non-streaming-asr-paraformer.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <RootNamespace>vad_non_streaming_asr_paraformer</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>