From ecc097f4820ce71c3ddfff24166962be4e03dded Mon Sep 17 00:00:00 2001
From: Sophia Tevosyan <stevosyan@microsoft.com>
Date: Wed, 29 Oct 2025 20:21:54 -0700
Subject: [PATCH 1/2] first commit

---
 .../ServiceCollectionExtensions.cs                    |  5 +++--
 .../ServiceCollectionExtensionsTests.cs               | 11 +++++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/Client/Core/DependencyInjection/ServiceCollectionExtensions.cs b/src/Client/Core/DependencyInjection/ServiceCollectionExtensions.cs
index 89d4db19..71e4459f 100644
--- a/src/Client/Core/DependencyInjection/ServiceCollectionExtensions.cs
+++ b/src/Client/Core/DependencyInjection/ServiceCollectionExtensions.cs
@@ -13,14 +13,15 @@ namespace Microsoft.DurableTask.Client;
 public static class ServiceCollectionExtensions
 {
     /// <summary>
-    /// Adds and configures Durable Task worker services to the service collection.
+    /// Configures and adds a <see cref="DurableTaskClient" /> to the service collection.
     /// </summary>
     /// <param name="services">The service collection to add to.</param>
     /// <param name="name">The name of the builder to add.</param>
     /// <returns>The builder used to configured the <see cref="DurableTaskClient"/>.</returns>
     public static IDurableTaskClientBuilder AddDurableTaskClient(this IServiceCollection services, string? name = null)
     {
-        Check.NotNull(services);
+        Check.NotNull(services);
+        services.TryAddSingleton<IDurableTaskClientProvider, DefaultDurableTaskClientProvider>();
         IDurableTaskClientBuilder builder = GetBuilder(services, name ?? Options.DefaultName, out bool added);
         ConditionalConfigureBuilder(services, builder, added);
         return builder;
diff --git a/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs b/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
index 7ddce4d5..a8dd68a7 100644
--- a/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
+++ b/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
@@ -121,6 +121,17 @@ public void AddDurableTaskClient_Named_HostedServiceAdded()
             x => x.ServiceType == typeof(IDurableTaskClientProvider) && x.Lifetime == ServiceLifetime.Singleton);
         services.Should().NotContain(
             x => x.ServiceType == typeof(DurableTaskClient) && x.Lifetime == ServiceLifetime.Singleton);
+    }
+
+    [Fact]
+    public void AddDurableTaskClient_Unnamed_HostedServiceAdded()
+    {
+        ServiceCollection services = new();
+        services.AddDurableTaskClient();
+        services.Should().ContainSingle(
+            x => x.ServiceType == typeof(IDurableTaskClientProvider) && x.Lifetime == ServiceLifetime.Singleton);
+        services.Should().ContainSingle(
+            x => x.ServiceType == typeof(DurableTaskClient) && x.Lifetime == ServiceLifetime.Singleton);
     }
 
     [Fact]

From f2beca47f60ca278ed927491f568286ae0d98727 Mon Sep 17 00:00:00 2001
From: Sophia Tevosyan <stevosyan@microsoft.com>
Date: Wed, 29 Oct 2025 20:33:29 -0700
Subject: [PATCH 2/2] added another null check and another unit test

---
 .../ServiceCollectionExtensions.cs                  |  3 ++-
 .../ServiceCollectionExtensionsTests.cs             | 13 +++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/Client/Core/DependencyInjection/ServiceCollectionExtensions.cs b/src/Client/Core/DependencyInjection/ServiceCollectionExtensions.cs
index 71e4459f..a1d96c5f 100644
--- a/src/Client/Core/DependencyInjection/ServiceCollectionExtensions.cs
+++ b/src/Client/Core/DependencyInjection/ServiceCollectionExtensions.cs
@@ -48,7 +48,8 @@ public static IServiceCollection AddDurableTaskClient(
     /// <returns>The original service collection, for call chaining.</returns>
     public static IServiceCollection AddDurableTaskClient(
         this IServiceCollection services, string name, Action<IDurableTaskClientBuilder> configure)
-    {
+    {
+        Check.NotNull(services);
         services.TryAddSingleton<IDurableTaskClientProvider, DefaultDurableTaskClientProvider>();
         IDurableTaskClientBuilder builder = GetBuilder(services, name, out bool added);
         configure.Invoke(builder);
diff --git a/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs b/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
index a8dd68a7..2dd643ac 100644
--- a/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
+++ b/test/Client/Core.Tests/DependencyInjection/ServiceCollectionExtensionsTests.cs
@@ -156,6 +156,19 @@ public void AddDurableTaskClient_DoesNotConfiguresConverter()
 
         DurableTaskClientOptions options = services.BuildServiceProvider().GetOptions<DurableTaskClientOptions>();
         options.DataConverter.Should().BeSameAs(JsonDataConverter.Default);
+    }
+
+    [Fact]
+    public void AddDurableTaskClient_NullServices_ThrowsException()
+    {
+        Action act = () => ((ServiceCollection)null!).AddDurableTaskClient();
+        act.Should().Throw<ArgumentNullException>();
+
+        act = () => ((ServiceCollection)null!).AddDurableTaskClient(builder => { });
+        act.Should().Throw<ArgumentNullException>();
+
+        act = () => ((ServiceCollection)null!).AddDurableTaskClient("name", builder => { });
+        act.Should().Throw<ArgumentNullException>();
     }
 
     class CustomDataConverter : DataConverter