[C#] Add ConfigureAwait to AsyncUnaryCall and AsyncClientStreamingCall (#28235)

* Add ConfigureAwait to AsyncUnaryCall and AsyncClientStreamingCall

* Update comment

src/csharp/Grpc.Core.Api/AsyncClientStreamingCall.cs

@@ -111,14 +111,27 @@ namespace Grpc.Core
         }
 
         /// <summary>
-        /// Allows awaiting this object directly.
+        /// Gets an awaiter used to await this <see cref="AsyncClientStreamingCall{TRequest,TResponse}"/>.
         /// </summary>
-        /// <returns></returns>
+        /// <returns>An awaiter instance.</returns>
+        /// <remarks>This method is intended for compiler use rather than use directly in code.</remarks>
         public TaskAwaiter<TResponse> GetAwaiter()
         {
             return responseAsync.GetAwaiter();
         }
 
+        /// <summary>
+        /// Configures an awaiter used to await this <see cref="AsyncClientStreamingCall{TRequest,TResponse}"/>.
+        /// </summary>
+        /// <param name="continueOnCapturedContext">
+        /// true to attempt to marshal the continuation back to the original context captured; otherwise, false.
+        /// </param>
+        /// <returns>An object used to await this task.</returns>
+        public ConfiguredTaskAwaitable<TResponse> ConfigureAwait(bool continueOnCapturedContext)
+        {
+            return responseAsync.ConfigureAwait(continueOnCapturedContext);
+        }
+
         /// <summary>
         /// Gets the call status if the call has already finished.
         /// Throws InvalidOperationException otherwise.

src/csharp/Grpc.Core.Api/AsyncUnaryCall.cs

@@ -93,13 +93,27 @@ namespace Grpc.Core
         }
 
         /// <summary>
-        /// Allows awaiting this object directly.
+        /// Gets an awaiter used to await this <see cref="AsyncUnaryCall{TResponse}"/>.
         /// </summary>
+        /// <returns>An awaiter instance.</returns>
+        /// <remarks>This method is intended for compiler use rather than use directly in code.</remarks>
         public TaskAwaiter<TResponse> GetAwaiter()
         {
             return responseAsync.GetAwaiter();
         }
 
+        /// <summary>
+        /// Configures an awaiter used to await this <see cref="AsyncUnaryCall{TResponse}"/>.
+        /// </summary>
+        /// <param name="continueOnCapturedContext">
+        /// true to attempt to marshal the continuation back to the original context captured; otherwise, false.
+        /// </param>
+        /// <returns>An object used to await this task.</returns>
+        public ConfiguredTaskAwaitable<TResponse> ConfigureAwait(bool continueOnCapturedContext)
+        {
+            return responseAsync.ConfigureAwait(continueOnCapturedContext);
+        }
+
         /// <summary>
         /// Gets the call status if the call has already finished.
         /// Throws InvalidOperationException otherwise.

src/csharp/Grpc.Core.Tests/ClientServerTest.cs

@@ -65,6 +65,8 @@ namespace Grpc.Core.Tests
             Assert.AreEqual("ABC", Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "ABC"));
 
             Assert.AreEqual("ABC", await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "ABC"));
+
+            Assert.AreEqual("ABC", await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "ABC").ConfigureAwait(false));
         }
 
         [Test]
@@ -197,12 +199,21 @@ namespace Grpc.Core.Tests
                 return result;
             });
 
-            var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall());
-            await call.RequestStream.WriteAllAsync(new string[] { "A", "B", "C" });
-            Assert.AreEqual("ABC", await call.ResponseAsync);
+            {
+                var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall());
+                await call.RequestStream.WriteAllAsync(new string[] { "A", "B", "C" });
+                Assert.AreEqual("ABC", await call);
+                Assert.AreEqual(StatusCode.OK, call.GetStatus().StatusCode);
+                Assert.IsNotNull(call.GetTrailers());
+            }
 
-            Assert.AreEqual(StatusCode.OK, call.GetStatus().StatusCode);
-            Assert.IsNotNull(call.GetTrailers());
+            {
+                var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall());
+                await call.RequestStream.WriteAllAsync(new string[] { "A", "B", "C" });
+                Assert.AreEqual("ABC", await call.ConfigureAwait(false));
+                Assert.AreEqual(StatusCode.OK, call.GetStatus().StatusCode);
+                Assert.IsNotNull(call.GetTrailers());
+            }
         }
 
         [Test]