Pro C# 5.0 and the .NET 4.5 Framework

This new edition of Pro C# 5.0 and the .NET 4.5 Platform has been completely revised and rewritten to reflect the latest changes to the C# language specification and new advances in the .NET Framework. 

Hosted Designer

What if we wanted to create a custom activity like the PrePostSequence and have someone else who does not have Visual Studio use it? Many products allow end users to customize workflows. Windows Workflow Foundation 4 allows us to host the designer in an application quite easily. In this article, we will host the designer and use your custom activity.

Activity Designers

As We have already seen Windows Workflow allows us to build custom activities in code.  There are several types of custom activities we can build depending on the base class.

Error Handling

In the previous post Adding If / Else Logic We may have noticed a potential bug in our simple application. What happens if we don't pass a UserName to the workflow? In this article, we will add some error handling capabilities to our workflow by using the Try/Catch, Catch<T> and Throw built-in activities.

Adding If / Else Logic

In the previous post Workflow Application part2 we created an enhanced Hello Workflow application with a custom hello message. In this post, we will add If/Else logic to the workflow to display a different Hello message depending on a custom condition.

Workflow Application part2

Our project is good but it has one weakness. It verifies that the WorkflowThread returned is non-zero but it does not verify that it returns the actual managed thread ID that the workflow ran on. Our project would pass if the workflow always returned 1.

Workflow Application part1

To this point we have focused on creating an activity and invoking it in the simplest way possible with the WorkflowInvoker class. The WorkflowInvoker.Invoke method is simple because it is synchronous and invokes the workflow on the same thread as the caller.

Testing Workflows

Up to this point the application is not very interesting. It is only working in a console and does not receive any input arguments. Most applications that do meaningful work will have to deal with input and output arguments. Additionally, the application is not easily tested in its current form.

Dynamic Workflows with XAML

Up to this point we have been authoring workflows in .xaml, .cs or .vb files. These files then get compiled into types that are included in the assembly of the project and run by the workflow runtime. 

The CodeActivity

We have open project from last post Refactoring Workflows as we seen on it, WF4 consists of a designer that edits .xaml files and a runtime that invokes activities. When we author a workflow, we are creating a new kind of activity and because activities are just classes that inherit from System.Activities.Activity or one of its subclasses, we can declare workflows using C#, VB or XAML. In this post, we will implement our “greeting” business process by creating an activity in C# or VB.

Refactoring Workflows

We will refactor the solution created in last post Hello Workflow . Even though we have a working application, we might want to make a few improvements. In this post, as Workflow1 is not a very descriptive name, you will change it to SayHello.

Hello Workflow

Creating a Simple Hello Workflow Application

We will create a very simple workflow that will be the equivalent to this code: