diff --git a/dotnet/src/Microsoft.Agents.AI.Workflows/SwitchBuilder.cs b/dotnet/src/Microsoft.Agents.AI.Workflows/SwitchBuilder.cs
index 0a6b9218f7..8141be1075 100644
--- a/dotnet/src/Microsoft.Agents.AI.Workflows/SwitchBuilder.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Workflows/SwitchBuilder.cs
@@ -36,10 +36,12 @@ public sealed class SwitchBuilder
         Throw.IfNull(executors);
 
         HashSet<int> indicies = [];
+        int executorIndex = 0;
 
         foreach (ExecutorBinding executor in executors)
         {
-            Throw.IfNull(executor);
+            Throw.IfNull(executor, $"{nameof(executors)}[{executorIndex}]");
+            executorIndex++;
 
             if (!this._executorIndicies.TryGetValue(executor.Id, out int index))
             {
@@ -66,9 +68,12 @@ public sealed class SwitchBuilder
     {
         Throw.IfNull(executors);
 
+        int executorIndex = 0;
+
         foreach (ExecutorBinding executor in executors)
         {
-            Throw.IfNull(executor);
+            Throw.IfNull(executor, $"{nameof(executors)}[{executorIndex}]");
+            executorIndex++;
 
             if (!this._executorIndicies.TryGetValue(executor.Id, out int index))
             {
diff --git a/dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/WorkflowBuilderSmokeTests.cs b/dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/WorkflowBuilderSmokeTests.cs
index 4997197445..c2b855b8bf 100644
--- a/dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/WorkflowBuilderSmokeTests.cs
+++ b/dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/WorkflowBuilderSmokeTests.cs
@@ -445,9 +445,9 @@ public partial class WorkflowBuilderSmokeTests
         // Act/Assert
         Assert.Throws<ArgumentNullException>("predicate", () => switchBuilder.AddCase<string>(null!, [target]));
         Assert.Throws<ArgumentNullException>("executors", () => switchBuilder.AddCase<string>(_ => true, null!));
-        Assert.Throws<ArgumentNullException>("executor", () => switchBuilder.AddCase<string>(_ => true, [target, null!]));
+        Assert.Throws<ArgumentNullException>("executors[1]", () => switchBuilder.AddCase<string>(_ => true, [target, null!]));
         Assert.Throws<ArgumentNullException>("executors", () => switchBuilder.WithDefault(null!));
-        Assert.Throws<ArgumentNullException>("executor", () => switchBuilder.WithDefault([target, null!]));
+        Assert.Throws<ArgumentNullException>("executors[1]", () => switchBuilder.WithDefault([target, null!]));
     }
 
     /// <summary>