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Adding a While Activity

Recall that our sequential process will prompt the end user for his or her name until the input can

be validated against a custom business rule (that is yet to be defined). Such looping behavior can be

represented using the While activity. Specifically, a While activity allows us to define a set of related

activities that will continuously execute until a specified condition is true.

To illustrate, begin by dragging a While activity from the Windows Workflow Toolbox directly

below the previous Code activity and rename this new activity to AskForNameLoopActivity. The

next step is to define the condition that will be used to exit the loop itself by setting the Condition

value from the Properties window. 

The Condition value (which is a common property of many activities) can be set in two key

ways. First of all, you can establish a 

code condition. As the name implies, this option allows you to

specify a method in your class that will be called by the activity in order to determine if it should

proceed. To inform the activity of this fact, the method specified will eventually need to return a

Boolean value (true to repeat, false to exit). 

The second way the Condition value can be set is by establishing a declarative rule condition.

This option can be useful in that you are able to specify a single code statement that evaluates to

true or false; however, this statement is not hard-coded in your assembly, but is instead offloaded

to a *.rules file. One benefit of this approach is that it makes it possible to modify rules in a declar-

ative manner.

Our condition will be based on some custom code that we have yet to author; however, the first

step is to select the Code Condition option from the Condition value, and then specify the name of

the method that will perform the test. Again using the Properties window, name this method

GetAndValidateUserName (see Figure 26-7).

As soon as you specify the name of the code condition used to test the While activity, the IDE

will generate a method stub where the second parameter is of type ConditionalEventArgs. This type

contains a property named Result, which can be set to true or false based on the success or failure

of the condition you are modeling. 

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