C# 4 and .NET 4

OC280 ❘ ChaPTer 57 windOws wOrkflOw fOundAtiOn 3.0
We begin with the canonical example that everyone uses when faced with a new technology — “Hello
World” — and also describe what you need to get workflows running on your development machine.
hello World
Visual Studio 2010 contains built-in support for creating workflows, and when you open the New Project
dialog, you see a list of workflow project types, as shown in Figure 57-1.
figure 57-1
Select Sequential Workflow Console Application from the available templates (that will
create a console application that hosts the workflow runtime) and a default workflow onto
which you can then drag and drop activities.
Next, drag a Code activity from the toolbox onto the design surface so that you have a
workflow that looks like the one shown in Figure 57-2.
The exclamation mark glyph on the top right of the activity indicates that a
mandatory property of that activity has not been defined — in this case, it is the
ExecuteCode property, which indicates the method that will be called when the activity figure 57-2
executes. You learn how to mark your own properties as mandatory in the section on
activity validation. If you double-click the code activity, a method will be created for you in the code-behind
class, and here you can use Console.WriteLine to output the “Hello World” string, as shown in the
following code snippet:
private void codeActivity1_ExecuteCode(object sender, EventArgs e)
{
Console.WriteLine("Hello World");
}
If you then build and run the program, you will see the output text on the console. When the program
executes, an instance of the WorkflowRuntime is created, and then an instance of your workflow is
constructed and executed. When the code activity executes, it calls the method defined and that outputs the
string to the console. The section entitled “The Workflow Runtime” later in the chapter describes in
detail how to host the runtime. The code for the preceding example is available in the 01 HelloWorkflow
World folder.
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