WF3.0 CallExternalMethod使用技巧

CallExternalMethod用于工作流向宿主进程中通信 简单的介绍一下它的使用技巧，参照网上的一个questioner源码进行了改进，因为我感觉这个源码提供的通信demo过于繁琐。

看看service代码

namespace QuestionService
{
    [ExternalDataExchange]
    public interface ITestService
    {
        void SendResponseDataToHost(TestPara responses);
    }
}

TestPara对象是对参数的一个封装，因为按照我的测试，在调用接口方法中，方法的参数如果不是对象类型，就会无法解决工作流传参的问题。

namespace QuestionService
{
    [Serializable]
    public class TestArgs : ExternalDataEventArgs
    {

        protected TestPara _dataValue = null;

        public TestPara Responses
        {
            get { return _dataValue; }
        }

        public TestArgs(Guid instanceId, TestPara responses)
            : base(instanceId)
        {
            _dataValue = responses;
        }

    }

    [Serializable]
    public class TestPara
    {
        protected bool[] _dataValue = null;

        public bool[] Responses
        {
            get { return _dataValue; }
            set { _dataValue = value; }
        }

    }
}

这是实现的关键地方，DataAvailable事件用于向宿主进程暴露

namespace QuestionService
{
    [Serializable]
    public class TestService : ITestService
    {

        #region ITestService 成员

        public event EventHandler<TestArgs> DataAvailable;

        public void SendResponseDataToHost(TestPara responses)
        {
            if (DataAvailable != null)
            {
                try
                {
                    DataAvailable(this, new TestArgs(WorkflowEnvironment.WorkflowInstanceId, responses));
                }
                catch (Exception ex)
                {

                }
            } // if
        }

        #endregion
    }
}

在工作流中  要设置相关的接口协议，选择调用的方法

需要注意的是 参数要在工作流中设置参数的属性 以供其选择，其中_response是工作流活动返回的数据，这里通过TestPara属性进行封装获取

        private bool[] _response = null;

        private TestPara _TestPara = new TestPara();
        public TestPara TestPara
        {
            get {
                _TestPara.Responses = _response;
                return _TestPara;
            }
        }

最后是宿主调用的过程  对调用进行了改动 DataAvailable事件暴露给宿主进程。以供工作流进程调用。

        private void cmdExecute_Click(object sender, EventArgs e)
        {
            // Disable the execute button
            cmdExecute.Enabled = false;

            // Clear the indicators
            ClearIndicators();

            // Set the cursor to "app starting"
            Cursor = Cursors.AppStarting;

            // Process the request, starting by creating the parameters
            Dictionary<string, object> parms = new Dictionary<string, object>();
            parms.Add("Dependent", cmbQuestionType.SelectedIndex == 0);
            string[] questions = new string[3];
            questions[0] = tbQuestion1.Text;
            questions[1] = tbQuestion2.Text;
            questions[2] = tbQuestion3.Text;
            parms.Add("Questions", questions);

            // Create instance.
            _workflowInstance = _workflowRuntime.CreateWorkflow(typeof(QuestionFlow.Workflow1), parms);
            if (_dataExchangeService==null)
            {
             _dataExchangeService = new ExternalDataExchangeService();
            _workflowRuntime.AddService(_dataExchangeService);
            TestService _testService = new TestService();
            _testService.DataAvailable += new EventHandler<QuestionService.TestArgs>(dataService_DataAvailable);
            _dataExchangeService.AddService(_testService);
            }

            // Hook returned data event
            //QuestionService.WorkflowResponseDataService dataService = QuestionService.WorkflowResponseDataService.CreateDataService(_workflowInstance.InstanceId, _workflowRuntime);

            // Start instance.
            _workflowInstance.Start();
        }

        public void dataService_DataAvailable(object sender, QuestionService.TestArgs e)
        {
            IAsyncResult result = this.BeginInvoke(
                new EventHandler(
                       delegate
                       {
                           // Retrieve connection.
                           //QuestionService.WorkflowResponseDataService dataService = QuestionService.WorkflowResponseDataService.GetRegisteredWorkflowDataService(e.InstanceId);

                           // Read the response data
                           bool[] responses = e.Responses.Responses;

                           // Bind the vehicles list to the vehicles table
                           SetIndicators(responses);
                       } // delegate
                    ), null, null
            ); // BeginInvoke
            this.EndInvoke(result);

            // Reset for next request
            WorkflowCompleted();
        }

        private delegate void WorkflowCompletedDelegate();

        private void WorkflowCompleted()
        {
            IAsyncResult result = this.BeginInvoke(
               new EventHandler(
                      delegate
                      {
                          // Reset the cursor
                          Cursor = Cursors.Arrow;

                          // Enable the execute button
                          cmdExecute.Enabled = true;
                      } // delegate
                   ), null, null
           ); // BeginInvoke
            this.EndInvoke(result);

        }