WF4:活动关联Activity correlation

Activity correlation：活动关联，确保两个活动一起工作。

当使用多个活动来完成单个操作时需要使用Activity correlation，WF4中的Send和ReceiveReply活动就是很好的例子。当我们使用ReceiveAndSendReply 或 SendAndReceiveReply 模板时，需要的活动的关联都已经自动的配置好了，但是如果我们在代码中使用Send 和 ReceiveReply或者 Receive 和SendReply活动时，就需要自己手动去实现，如没有改关联会有下面异常：System.InvalidOperationException：

The Send activity is configured with a request/reply Operation 'GetData', however, there is no ReceiveReply activity paired with it. Please pair Send with ReceiveReply and correlate them using a CorrelationHandle.

有不同的方式来配置活动关联，第一种就是使用CorrelationScope活动，CorrelationScope会自动的创建所需要的关联句柄，并且消息活动将会使用这个句柄。

下面是例子：

 

static Activity CreateWorkflow()
{
    var getDataResult = new Variable<string>();
    var handel = new Variable<CorrelationHandle>();

    var send = new Send()
    {
        CorrelationInitializers =
        {
            new RequestReplyCorrelationInitializer()
            {
                CorrelationHandle = handel
            }
        },
        OperationName = "GetData",
        ServiceContractName = "IService1",
        Endpoint = new Endpoint()
        {
            Binding = new BasicHttpBinding(),
            AddressUri = new Uri("http://localhost:8080/GetDataService/")
        },
        Content = new SendParametersContent()
        {
            Parameters =
            {
                {"value", new InArgument<int>(42)}
            }
        }
    };

    var receive = new ReceiveReply()
    {
        Request = send,
        Content = new ReceiveParametersContent
        {
            Parameters =
            {
                {"GetDataResult", new OutArgument<string>(getDataResult)}
            }
        }
    };

    var workflow = new Sequence()
    {
        Variables = { getDataResult, handel },
        Activities =
        {
            send,
            receive,
            new WriteLine() { Text = getDataResult }
        }
    };

    return workflow;
}

 

上面我们是使用RequestReplyCorrelationInitializer，我们还可以使用CorrelationScope来完成同样的事情，创建同样的工作流，如下：

static Activity CreateWorkflow()
{
    var getDataResult = new Variable<string>();

    var send = new Send()
    {
        OperationName = "GetData",
        ServiceContractName = "IService1",
        Endpoint = new Endpoint()
        {
            Binding = new BasicHttpBinding(),
            AddressUri = new Uri("http://localhost:8080/GetDataService/")
        },
        Content = new SendParametersContent()
        {
            Parameters =
            {
                {"value", new InArgument<int>(42)}
            }
        }
    };

    var receive = new ReceiveReply()
    {
        Request = send,
        Content = new ReceiveParametersContent
        {
            Parameters =
            {
                {"GetDataResult", new OutArgument<string>(getDataResult)}
            }
        }
    };

    var workflow = new Sequence()
     {
         Variables = { getDataResult },
         Activities =
        {
            new CorrelationScope()
            {
                Body = new Sequence()
                {
                    Activities = { send, receive }
                }
            },
            new WriteLine() { Text = getDataResult } }
     };

    return workflow;
}