Windows workflow example 4.0

Download Microsoft Edge More info. Contents Exit focus mode. Is this page helpful? Please rate your experience Yes No. Any additional feedback? Submit and view feedback for This product This page. View all page feedback. It also contained the definition of the class members and the event handler code. In WF 4. There is no longer a state machine workflow. Added use of variables and arguments because there is no code file.

There is no WorkflowRuntime class. Previously, you would have created the WorkflowRuntime class and then called its CreateWorkflow method. With WF 4. Variables are like class members to store data that can be shared between activities. Create argument OrderInfo of type Order class. Arguments are similar to variables, but they are intended for passing data in or out of the workflow.

You can think of them as method parameters. A workflow is defined using only XAML. We can still use code though by creating a custom activity. Figure 3. WF4 Out of the Box Activities. At first glance, we can easily guess what some of these activities do. I noticed that exception handling is a bit different now. There are the TryCatch, Throw and Rethrow activities. In WF3, exception handling is done by using fault handlers and fault handler activities.

If you are reviewing your workflow, these things are very easy to miss. There are also collection activities which allow you to add, clear, remove items or check if an item is in a collection. The Assign activity is like an assignment statement.

The Delay activity, which is also available in WF3, delays execution for a specified period of time. The InvokeMethod activity lets you execute the method of an object. There is the WriteLine activity, for easy output. I believe that these are provided as out of the box activities because there is no code-beside logic, and the said operations are commonly used. Other things that are new to me are activities regarding migration and runtime operations.

Migration is new because it is the one that lets a workflow use WF3 activities, by using the Interop activity. Meanwhile, runtime operations include persisting and terminating a workflow.

Getting Started with Workflows. First, create a project of type workflow console application. There are 3 files created automatically: the application configuration file, the file containing the main method, and the workflow file. First, the workflow should accept a string input. Open the workflow in the WF designer. You can see three buttons on the lower left portion of the designer: Variables, Arguments, and Imports.

Click on the Arguments button and add the StringToReverse argument. Another argument we need to add is an out parameter where the reversed string will be stored.

Figure 4. Defining the Arguments. Note that WF4 uses Visual Basic expressions. For example, if we want to set the default value of the StringToReverse argument to null, we have to set the value to Nothing. Going back, our algorithm for reversing the string is to define a variable and append the characters of the string starting from the last. The StringBuilder class will do the job. To use the StringBuilder class, we need to import the namespace where the class can be found, which is the System.

Text namespace. If you click on the Imports button, you will see that the System. Text namespace is already included in the list. To define the StringBuilder variable, we first need to add an activity to our workflow. The activity will serve as the scope of the variable. We need to add a Sequence activity since we will add a sequence of activities to it later on. We will use the While activity to iterate over the characters of the input string. Meanwhile, the Assign activity will be used to assign the out parameter to the reversed string.

Figure 5. Defining the Variables. Select the Sequence activity, click on the Variables button and add the StringBuilder variable like in Figure 5. To specify the variable type, you must know the assembly where the type is located. After this, add another Sequence activity, this time inside the body of the While activity.

The first one will be done by using an Assign activity while the second requires an InvokeMethod activity, which is used in calling the Append method of the StringBuilder object.

Figure 6. The TargetType and TargetObject properties cannot be set at the same time. You should set the TargetType if you want to call a static method. Otherwise, set the TargetObject to call an instance method.

Now, set the MethodName to Append. To set the parameters of the method, we need to set the Parameters property in the Properties window in Visual Studio.

Figure 7. InvokeMethod Activity Properties. Here, you can see all the properties for the activity currently selected. Now, set the parameters by clicking on the button with the ellipsis. A dialog will be shown where the parameters can be added. You can specify the direction, type of the parameter and the value. In our example, the value is set to a character in the StringToReverse string, obtained using the Counter variable as the index.

Figure 8. Setting Method Parameters. All that is left is to return the reversed string.