Guard against null passwords 2/2

Author: Nuklon

src/Wpf.Ui/Controls/PasswordBox/PasswordHelper.cs

@@ -19,8 +19,8 @@ private class PasswordHelper
     {
         private readonly PasswordBox _passwordBox;
         private string _currentText;
-        private string _newPassword;
-        private string _currentPassword;
+        private string? _newPassword;
+        private string? _currentPassword;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="PasswordHelper"/> class.
@@ -44,7 +44,7 @@ public PasswordHelper(PasswordBox passwordBox)
         /// 2. When password is revealed (plain text mode)
         /// 3. When password is hidden (masked character mode)
         /// </remarks>
-        public string GetNewPassword()
+        public string? GetNewPassword()
         {
             _currentPassword = _passwordBox.Password;
             _newPassword = _currentPassword;
@@ -53,8 +53,8 @@ public string GetNewPassword()
 
             if (IsDeletingText())
             {
-                int charsToRemove = _currentPassword.Length - _currentText.Length;
-                _newPassword = _currentPassword.Remove(selectionIndex, charsToRemove);
+                int charsToRemove = (_currentPassword?.Length ?? 0) - _currentText.Length;
+                _newPassword = _currentPassword?.Remove(selectionIndex, charsToRemove);
                 return _newPassword;
             }
 
@@ -78,26 +78,26 @@ public string GetNewPassword()
         /// 2. Character was replaced (overwrite)
         /// 3. Characters were removed
         /// </remarks>
-        private string HandleHiddenModeChanges(int selectionIndex)
+        private string? HandleHiddenModeChanges(int selectionIndex)
         {
             char passwordChar = _passwordBox.PasswordChar;
-            int currentLength = _currentPassword.Length;
+            int currentLength = _currentPassword?.Length ?? 0;
 
             if (_currentText.Length > currentLength)
             {
                 // Characters were inserted
                 int insertedCount = _currentText.Length - currentLength;
                 string insertedText = _currentText.Substring(selectionIndex - insertedCount, insertedCount);
-                _newPassword = _currentPassword.Insert(selectionIndex - insertedCount, insertedText);
+                _newPassword = _currentPassword?.Insert(selectionIndex - insertedCount, insertedText);
             }
             else if (_currentText.Length == currentLength)
             {
                 // Character was replaced (overwrite)
                 for (int i = 0; i < _currentText.Length; i++)
                 {
-                    if (_currentText[i] != passwordChar && i < _newPassword.Length)
+                    if (_currentText[i] != passwordChar && i < (_newPassword?.Length ?? 0))
                     {
-                        _newPassword = _newPassword.Remove(i, 1).Insert(i, _currentText[i].ToString());
+                        _newPassword = _newPassword?.Remove(i, 1).Insert(i, _currentText[i].ToString());
                         break;
                     }
                 }
@@ -106,7 +106,7 @@ private string HandleHiddenModeChanges(int selectionIndex)
             {
                 // Characters were removed (fallback)
                 int removedCount = currentLength - _currentText.Length;
-                _newPassword = _currentPassword.Remove(selectionIndex, removedCount);
+                _newPassword = _currentPassword?.Remove(selectionIndex, removedCount);
             }
 
             return _newPassword;
@@ -121,7 +121,7 @@ private bool IsDeletingText()
             Debug.Assert(_currentText == _passwordBox.Text, "Text mismatch");
             Debug.Assert(_currentPassword == _passwordBox.Password, "Password mismatch");
 
-            return _currentText.Length < _currentPassword.Length;
+            return _currentText.Length < (_currentPassword?.Length ?? 0);
         }
     }
 }