Avoid more UnobservedTaskExceptions in SignalR .NET client (#46781)

Author: BrennanConroy

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

@@ -322,5 +322,8 @@ public static void ErrorHandshakeTimedOut(ILogger logger, TimeSpan handshakeTime
 
         [LoggerMessage(88, LogLevel.Warning, "Error returning result for invocation '{InvocationId}' for method '{Target}' because the underlying connection is closed.", EventName = "ErrorSendingInvocationResult")]
         public static partial void ErrorSendingInvocationResult(ILogger logger, string invocationId, string target, Exception exception);
+
+        [LoggerMessage(89, LogLevel.Trace, "Error sending Completion message for stream '{StreamId}'.", EventName = "ErrorSendingStreamCompletion")]
+        public static partial void ErrorSendingStreamCompletion(ILogger logger, string streamId, Exception exception);
     }
 }

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

@@ -641,14 +641,17 @@ async Task OnStreamCanceled(InvocationRequest irq)
                 {
                     Log.SendingCancellation(_logger, irq.InvocationId);
 
-                    // Fire and forget, if it fails that means we aren't connected anymore.
-                    _ = SendHubMessage(_state.CurrentConnectionStateUnsynchronized, new CancelInvocationMessage(irq.InvocationId), irq.CancellationToken);
+                    await SendHubMessage(_state.CurrentConnectionStateUnsynchronized, new CancelInvocationMessage(irq.InvocationId), irq.CancellationToken).ConfigureAwait(false);
                 }
                 else
                 {
                     Log.UnableToSendCancellation(_logger, irq.InvocationId);
                 }
             }
+            catch
+            {
+                // Connection closed while trying to cancel a stream. This is fine to ignore.
+            }
             finally
             {
                 _state.ReleaseConnectionLock();
@@ -849,6 +852,10 @@ private async Task CommonStreaming(ConnectionState connectionState, string strea
                 Log.CompletingStreamNotSent(_logger, streamId);
             }
         }
+        catch (Exception ex)
+        {
+            Log.ErrorSendingStreamCompletion(_logger, streamId, ex);
+        }
         finally
         {
             _state.ReleaseConnectionLock();
@@ -1996,6 +2003,10 @@ internal async Task RunTimerActions()
                         await _hubConnection.SendHubMessage(this, PingMessage.Instance).ConfigureAwait(false);
                     }
                 }
+                catch
+                {
+                    // The exception from send should be seen elsewhere in the client. We'll ignore it here.
+                }
                 finally
                 {
                     _hubConnection._state.ReleaseConnectionLock();