Add additional check for closed/broken connection errors (#862)

Author: Charles-Gagnon

src/SqlBindingUtilities.cs

@@ -250,8 +250,16 @@ internal static async Task OpenAsyncWithSqlErrorHandling(this SqlConnection conn
         /// <returns>True if the exception is a fatal SqlClientException, false otherwise</returns>
         internal static bool IsFatalSqlException(this Exception e)
         {
+            string lowerMessage = e.Message.ToLowerInvariant();
             // Most SqlExceptions wrap the original error from the native driver, so make sure to check both
-            return (e as SqlException)?.Class >= 20 || (e.InnerException as SqlException)?.Class >= 20;
+            return (e as SqlException)?.Class >= 20
+                || (e.InnerException as SqlException)?.Class >= 20
+                // TEMPORARY - Not all exceptions thrown by SqlClient are SqlExceptions, and the current SqlClient
+                // does not correctly update the State property in all cases. So for now explicitly check for
+                // the string containing a message indicating that the connection has been closed or broken.
+                // This should be removed once version 5.2.0+ has been released
+                // https://github.com/Azure/azure-functions-sql-extension/issues/860
+                || (lowerMessage.Contains("connection") && (lowerMessage.Contains("broken") || lowerMessage.Contains("closed")));
         }
 
         /// <summary>