WF Series 3-CallExternalMethod Activity

Series Directory: WF Series 3 Out-of-the-Box Activities topic directory

3.2.1 CallExternalMethod Activity

CallExternalMethod Activity is an important component in the local communication service.
To use this Activity, you must set two attributes:

• InterfaceType: Specifies the interface used to define workflow communication.
• MethodName: Specifies the method to be called.

Citation:

Why is CallExternalMethod limited to methods that call known interfaces?
The reason is that the activity is not just a code performer, but a two-way communication with the local service is implemented together with the HandleExternalEvent activity. With the CallExternalMethod activity, you can call a service method to process events triggered by a service by adding HandleExternalEvent to a workflow.

Example:

1. Create a Sequential Workflow project

----- Drag CallExternalMethodActivity into Workflow

2. Create an interface File

3. Set the InterfaceType and MethodName attributes.

---- Set InterfaceType to InterfaceCode

---- Set MethodName to interfaceMethod

---- Print the predefined statement "invoke interfaceMethod"

* See, pay attention to this sentence: [Showing interfaces marked withExternalDataExchangeAttribute]

If [ExternalDataExchange] is not added to an Interface, no Interface is available.

Why should I add [ExternalDataExchange]?

It is necessary to declare the service interface. Otherwise, the service cannot be added to the process.

Private void callExternalMethodActivity1_MethodInvoking (object sender, EventArgs e)
{
Console. WriteLine ("execute CallExternalMethod Activity ");
}

The Main code is as follows:

Static void Main ()
{
Using (WorkflowRuntime workflowRuntime = new WorkflowRuntime ())
{
ExternalDataExchangeService dataService = new ExternalDataExchangeService ();
WorkflowRuntime. AddService (dataService );
DataService. AddService (new Serivces ());

WorkflowRuntime. StartRuntime ();

AutoResetEvent waitHandle = new AutoResetEvent (false );
WorkflowRuntime. WorkflowCompleted + = delegate (object sender, WorkflowCompletedEventArgs e) {waitHandle. Set ();};

WorkflowInstance instance = workflowRuntime. CreateWorkflow (typeof (DemoCallExternalMethodActivity ));
Instance. Start ();

WaitHandle. WaitOne ();

WorkflowRuntime. StopRuntime ();
}
}

Public class Serivces: InterfaceCode
{
InterfaceCode Members # region InterfaceCode Members

Public void interfaceMethod ()
{
Console. WriteLine ("invoke interfaceMethod ");
}

# Endregion
}

Someone also asked me: why do CallExternalMethodActivity and HandleExternalEventactivity often work together?

A: CallExternalMethodActivity is an execution action.

HandleExternalEventactivity is an event action

Therefore, the execution behavior usually triggers the event behavior. [Explanation of process ideas]

Attached with the CallExternalMethodActivity Application

Download DEMO