Adding lambda condition to .NET AP

dotnet/src/Microsoft.AutoGen/AgentChat/Terminations/LambdaTerminationCondition.cs

@@ -0,0 +1,45 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// LambdaTerminationCondition.cs
+using Microsoft.AutoGen.AgentChat.Abstractions;
+
+namespace Microsoft.AutoGen.AgentChat.Terminations;
+
+/// <summary>
+/// A termination condition that evaluates a lambda function against the latest ChatMessage.
+/// </summary>
+public sealed class LambdaTerminationCondition : ITerminationCondition
+{
+    private readonly Func<ChatMessage, bool> _condition;
+    public bool IsTerminated { get; private set; }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="LambdaTerminationCondition"/> class.
+    /// </summary>
+    /// <param name="condition">A lambda function that takes a <see cref="ChatMessage"/> and returns a boolean indicating if the termination condition is met.</param>
+    public LambdaTerminationCondition(Func<ChatMessage, bool> condition)
+    {
+        _condition = condition ?? throw new ArgumentNullException(nameof(condition));
+        IsTerminated = false;
+    }
+
+    public ValueTask<StopMessage?> CheckAndUpdateAsync(IList<AgentMessage> messages)
+    {
+        if (IsTerminated)
+        {
+            throw new TerminatedException();
+        }
+
+        // Find the latest ChatMessage
+        for (int i = messages.Count - 1; i >= 0; i--)
+        {
+            if (messages[i] is ChatMessage chatMsg && _condition(chatMsg))
+            {
+                IsTerminated = true;
+                return ValueTask.FromResult<StopMessage?>(new StopMessage { Content = "Lambda termination condition met.", Source = nameof(LambdaTerminationCondition) });
+            }
+        }
+        return ValueTask.FromResult<StopMessage?>(null);
+    }
+
+    public void Reset() => IsTerminated = false;
+}