The synchronous OperationContract method '{0}' in type '{1}' was matched with the task-based asynchronous OperationContract ...

The synchronous OperationContract method '{0}' in type '{1}' was matched with the task-based asynchronous OperationContract method '{2}' because they have the same operation name '{3}'. When a synchronous OperationContract method is matched to a task-based asynchronous OperationContract method, any additional attributes must be declared on the synchronous OperationContract method. In this case, the task-based asynchronous OperationContract method '{2}' has one or more attributes of type '{4}'. To fix it, remove the '{4}' attribute or attributes from method '{2}'. Alternatively, changing the name of one of the methods will prevent matching.