Avoid UnobservedTaskExceptions when getting an error in server to client streaming (dotnet#46198)

Author: BrennanConroy

src/SignalR/clients/csharp/Client.Core/src/HubConnection.cs

@@ -611,13 +611,22 @@ public virtual IAsyncEnumerable<TResult> StreamAsyncCore<TResult>(string methodN
     private async IAsyncEnumerable<T> CastIAsyncEnumerable<T>(string methodName, object?[] args, CancellationTokenSource cts)
     {
         var reader = await StreamAsChannelCoreAsync(methodName, typeof(T), args, cts.Token).ConfigureAwait(false);
-        while (await reader.WaitToReadAsync(cts.Token).ConfigureAwait(false))
+
+        try
         {
-            while (reader.TryRead(out var item))
+            while (await reader.WaitToReadAsync(cts.Token).ConfigureAwait(false))
             {
-                yield return (T)item!;
+                while (reader.TryRead(out var item))
+                {
+                    yield return (T)item!;
+                }
             }
         }
+        finally
+        {
+            // Needed to avoid UnobservedTaskExceptions
+            _ = reader.Completion.Exception;
+        }
     }
 
     private async Task<ChannelReader<object?>> StreamAsChannelCoreAsyncCore(string methodName, Type returnType, object?[] args, CancellationToken cancellationToken)

src/SignalR/clients/csharp/Client.Core/src/HubConnectionExtensions.StreamAsChannelAsync.cs

@@ -302,9 +302,6 @@ private static async Task RunChannel<TResult>(ChannelReader<object?> inputChanne
                     }
                 }
             }
-
-            // Manifest any errors in the completion task
-            await inputChannel.Completion.ConfigureAwait(false);
         }
         catch (Exception ex)
         {
@@ -314,6 +311,9 @@ private static async Task RunChannel<TResult>(ChannelReader<object?> inputChanne
         {
             // This will safely no-op if the catch block above ran.
             outputChannel.Writer.TryComplete();
+
+            // Needed to avoid UnobservedTaskExceptions
+            _ = inputChannel.Completion.Exception;
         }
     }
 }