What Are Communication Activities? (From Microsoft Elearning)

What Are Communication Activities?

WF communication activities send data to, and receive data from, external sources. These sources can include databases, Web services, and e-mail servers. Such activities are fundamental to most workflows. For example, conditional activities may have conditions that check data in a database. The following sections describe frequently used communication activities:

InvokeWebServiceActivity

The InvokeWebServiceActivity invokes a Web service through a proxy class, passing and receiving specified parameters. When you use the InvokeWebServiceActivity, you must specify the proxy class to use by setting the ProxyClass property. You must also specify the Web service method that you want to call by setting the MethodName property.

CallExternalMethodActivity

You can use the CallExternalMethodActivity to communicate with a local service. A local service is a .NET Framework class that implements the ICommunicationService interface.

HandleExternalEventActivity

You can use the HandleExternalEventActivity to handle events from a local service. Usually, the CallExternalMethodActivity calls the local service and send parameters to it. When the external method completes, it raises an event that you handle with HandleExternalEventActivity.

Before you start an instance of your workflow, you must add the ExternalDataExchangeService to the workflow runtime engine and then add your custom communication service to the ExternalDataExchangeService.

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