Fix streaming wording and example (#19984)

Author: BrennanConroy

aspnetcore/signalr/streaming.md

@@ -58,7 +58,7 @@ The following sample shows the basics of streaming data to the client using Chan
 > [!NOTE]
 > Write to the `ChannelWriter<T>` on a background thread and return the `ChannelReader` as soon as possible. Other hub invocations are blocked until a `ChannelReader` is returned.
 >
-> Wrap logic in a `try ... catch`. Complete the `Channel` in the `catch` and outside the `catch` to make sure the hub method invocation is completed properly.
+> Wrap logic in a [`try ... catch` statement](/dotnet/csharp/language-reference/keywords/try-catch). Complete the `Channel` in a [`finally` block](/dotnet/csharp/language-reference/keywords/try-catch-finally). If you want to flow an error, capture it inside the `catch` block and write it in the `finally` block.
 
 ::: moniker range=">= aspnetcore-3.0"
 

aspnetcore/signalr/streaming/samples/2.1/Hubs/StreamHub.cs

@@ -27,6 +27,7 @@ private async Task WriteItemsAsync(
             int count,
             int delay)
         {
+            Exception localException = null;
             try
             {
                 for (var i = 0; i < count; i++)
@@ -37,10 +38,13 @@ private async Task WriteItemsAsync(
             }
             catch (Exception ex)
             {
-                writer.TryComplete(ex);
+                localException = ex;
+            }
+            finally
+            {
+                writer.Complete(localException);
             }
 
-            writer.TryComplete();
         }
     }
     #endregion

aspnetcore/signalr/streaming/samples/2.2/Hubs/StreamHub.cs

@@ -32,6 +32,7 @@ private async Task WriteItemsAsync(
             int delay,
             CancellationToken cancellationToken)
         {
+            Exception localException = null;
             try
             {
                 for (var i = 0; i < count; i++)
@@ -48,10 +49,12 @@ private async Task WriteItemsAsync(
             }
             catch (Exception ex)
             {
-                writer.TryComplete(ex);
+                localException = ex;
+            }
+            finally
+            {
+                writer.Complete(localException);
             }
-
-            writer.TryComplete();
         }
     }
     #endregion

aspnetcore/signalr/streaming/samples/3.0/Hubs/StreamHub.cs

@@ -48,8 +48,10 @@ private async Task WriteItemsAsync(
             {
                 localException = ex;
             }
-
-            writer.Complete(localException);
+            finally
+            {
+                writer.Complete(localException);
+            }
         }
         #endregion