dotnet: update README attachment examples to use AttachmentFile/AttachmentBlob; fix Session example (fixes #2196 (#2208)

Author: HindzStark

dotnet/README.md

@@ -296,9 +296,9 @@ The SDK supports image attachments via the `Attachments` parameter. You can atta
 await session.SendAsync(new MessageOptions
 {
     Prompt = "What's in this image?",
-    Attachments = new List<UserMessageDataAttachmentsItem>
+    Attachments = new List<Attachment>
     {
-        new UserMessageDataAttachmentsItemFile
+        new AttachmentFile
         {
             Path = "/path/to/image.jpg",
             DisplayName = "image.jpg",
@@ -310,9 +310,9 @@ await session.SendAsync(new MessageOptions
 await session.SendAsync(new MessageOptions
 {
     Prompt = "What's in this image?",
-    Attachments = new List<UserMessageDataAttachmentsItem>
+    Attachments = new List<Attachment>
     {
-        new UserMessageDataAttachmentsItemBlob
+        new AttachmentBlob
         {
             Data = base64ImageData,
             MimeType = "image/png",
@@ -721,13 +721,12 @@ await session2.SendAsync(new MessageOptions { Prompt = "Hello from session 2" })
 await session.SendAsync(new MessageOptions
 {
     Prompt = "Analyze this file",
-    Attachments = new List<UserMessageDataAttachmentsItem>
+    Attachments = new List<Attachment>
     {
-        new UserMessageDataAttachmentsItem
+        new AttachmentFile
         {
-            Type = UserMessageDataAttachmentsItemType.File,
             Path = "/path/to/file.cs",
-            DisplayName = "My File"
+            DisplayName = "My File",
         }
     }
 });

dotnet/src/Session.cs

@@ -1,4 +1,4 @@
-/*---------------------------------------------------------------------------------------------
+/*---------------------------------------------------------------------------------------------
  *  Copyright (c) Microsoft Corporation. All rights reserved.
  *--------------------------------------------------------------------------------------------*/
 
@@ -263,7 +263,7 @@ public Task<string> SendAsync(string prompt, CancellationToken cancellationToken
     ///     Prompt = "Explain this code",
     ///     Attachments = new List&lt;Attachment&gt;
     ///     {
-    ///         new() { Type = "file", Path = "./Program.cs" }
+    ///         new AttachmentFile { Path = "./Program.cs", DisplayName = "Program.cs" }
     ///     }
     /// });
     /// </code>