At least one operation on the '{0}' contract is configured with the TransactionFlowAttribute attribute set to Mandatory but ...

At least one operation on the '{0}' contract is configured with the TransactionFlowAttribute attribute set to Mandatory but the channel's binding '{1}' is not configured with a TransactionFlowBindingElement. The TransactionFlowAttribute attribute set to Mandatory cannot be used without a TransactionFlowBindingElement.