Address code review feedback

dotnet/src/Connectors/Connectors.MistralAI.UnitTests/MistralAIPromptExecutionSettingsTests.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System;
 using System.Text.Json;
 using Microsoft.SemanticKernel;
 using Microsoft.SemanticKernel.Connectors.MistralAI;
@@ -68,4 +69,44 @@ public void FromExecutionSettingsWhenSerializedHasPropertiesShouldPopulateSpecia
         Assert.True(MistralExecutionSettings.SafePrompt);
         Assert.Equal(123, MistralExecutionSettings.RandomSeed);
     }
+
+    [Fact]
+    public void FreezeShouldPreventPropertyModification()
+    {
+        // Arrange  
+        var settings = new MistralAIPromptExecutionSettings
+        {
+            Temperature = 0.7,
+            TopP = 1,
+            MaxTokens = 100,
+            SafePrompt = false,
+            Stop = ["foo", "bar"]
+        };
+
+        // Act  
+        settings.Freeze();
+
+        // Assert  
+        // Try to modify a property after freezing  
+        Assert.Throws<InvalidOperationException>(() => settings.Temperature = 0.8);
+        Assert.Throws<InvalidOperationException>(() => settings.TopP = 0.9);
+        Assert.Throws<InvalidOperationException>(() => settings.MaxTokens = 50);
+        Assert.Throws<InvalidOperationException>(() => settings.SafePrompt = true);
+        Assert.Throws<NotSupportedException>(() => settings.Stop.Add("baz"));
+    }
+
+    [Fact]
+    public void FreezeShouldNotAllowMultipleFreezes()
+    {
+        // Arrange  
+        var settings = new MistralAIPromptExecutionSettings();
+        settings.Freeze(); // First freeze  
+
+        // Act  
+        settings.Freeze(); // Second freeze (should not throw)  
+
+        // Assert  
+        // No exception should be thrown  
+        Assert.True(settings.IsFrozen); // Assuming IsFrozen is a property indicating the freeze state  
+    }
 }

dotnet/src/Connectors/Connectors.MistralAI/Client/ContentChunkType.cs

@@ -43,7 +43,7 @@ public ContentChunkType(string type)
     /// <param name="right"> the second <see cref="ContentChunkType"/> instance to compare </param>
     /// <returns> false if left and right are both null or have equivalent labels; true otherwise </returns>
     public static bool operator !=(ContentChunkType left, ContentChunkType right)
-        => !(left == right);
+        => !left.Equals(right);
 
     /// <inheritdoc/>
     public override bool Equals([NotNullWhen(true)] object? obj)

dotnet/src/Connectors/Connectors.MistralAI/MistralAIPromptExecutionSettings.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 using Microsoft.SemanticKernel.ChatCompletion;
@@ -247,6 +248,11 @@ public override void Freeze()
             return;
         }
 
+        if (this._stop is not null)
+        {
+            this._stop = new ReadOnlyCollection<string>(this._stop);
+        }
+
         base.Freeze();
     }
 
@@ -267,7 +273,7 @@ public override PromptExecutionSettings Clone()
             ResponseFormat = this.ResponseFormat,
             FrequencyPenalty = this.FrequencyPenalty,
             PresencePenalty = this.PresencePenalty,
-            Stop = this.Stop,
+            Stop = this.Stop is not null ? new List<string>(this.Stop) : null,
         };
     }