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Hello World Custom Activity

This topic applies to Windows Workflow Foundation 4 (WF4).

This sample demonstrates several key features of Windows Workflow Foundation (WF), including how to create a simple custom activity. Some of the features demonstrated in this sample are creating a custom activity in C# and using in and out arguments (InArgument and OutArgument).

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Creating a Workflow in Code

In this sample, two custom activities are created using C# code. Both custom activities inherit directly or indirectly from Activity to return a single value. The advantage of using the generic return value, instead of inheriting from the non-generic Activity class, is that some activities (such as Assign) are able to access the return value when used as part of a composed activity.

This activity inherits from Activity, and uses an Assign activity that concatenates two strings together.

Prepend String
This activity inherits directly from CodeActivity, and creates similar functionality to the AppendString activity, which uses logic implemented in code rather than being composed of a pre-existing activity.

The following files are included in this project.

The custom activity that appends strings together. It takes in a string and combines it with a literal text string “ says hello world” to form a complete message as output.

This activity prefixes a predefined string to an input string.

A workflow that uses the AppendString and PrependString custom activities.

A program that runs the workflow.

To use this sample

  1. Using Visual Studio 2010, open the HelloWorld.sln solution file.

  2. To build the solution, press CTRL+SHIFT+B.

  3. To run the solution, press F5.