MSDN Magazine - August 2008 - (Page 109)

MATT Milner Foundations Workflow Tips And Tricks As an author and instructor, I often get asked questions about Windows® Workflow Foundation (WF) that do not require enough depth to warrant an entire column. However, the responses and techniques have proven to be useful to many developers and often can be used in a wide variety of scenarios. This month I will cover several different topics, some that are intended to address specific reader questions, such as how to safely share Figure 1 Switch Activity with and without a Custom Toolbox Item a persistence database across apps, and others that show how to leverage parts of the framework that do one who did not know about the activity would likely think there not get much coverage, such as the ChannelManagerService. was a problem with it, as there would be no indication of where to put his custom logic. The toolbox item allowed me to initialize the Creating Template Activities switch activity with two branches so the user would know where to One common request from developers is to be able to create ac- begin customizing the activity, as shown in Figure 1. tivity templates. People are looking for a way to create most of the The switch activity is a composite activity that provides control logic in an activity but leave some extensibility points for consum- flow logic but not any custom business logic. Simple composite acers of the activity to fill in with their own activities. Unfortunately, tivities, the kind you get when you choose to add a new activity to Windows WF does not support that model directly, but there are your project, generally derive from the SequenceActivity class and two alternative options that work in many scenarios. rely on contained activities to define business process logic. The first option is to create a Visual Studio® new-item template An example of this type of composite activity would be a managthat contains the template structure of your activity, and then let er-approval process where the general process is reusable, but the the users add that new item to their project and customize it. In individual steps can vary for each process instance. You might, for this scenario, developers are the expected user because the solution example, want to create a template that consists of resolving manrequires Visual Studio to create an activity from the template and a ager details such as e-mail or instant messenger address, sending compiler to build the new activity so that it can be used. him a message, and handling all errors around those steps. You I wrote about creating custom templates in Visual Studio in the might also want to allow someone to customize this process so he January 2006 issue of MSDN® Magazine (msdn.microsoft.com/magazine/ can more easily manipulate the message being sent or the paramcc188697), so I will not spend time on the details here. The benefit of eters around how it should be sent. this model is that it leverages the tools available and provides a quick Included in the code download for this column are a few sample way to ensure a consistent base structure for your activities. activities including simple activity stubs for getting manager details The second option for creating a template is to build a custom and sending an instant message (IM). The included NotifyManagertoolbox item that can create the template when the user drags an ActivityToolboxItem creates activities, adds error handling, and item onto the Workflow Designer surface. In the December 2006 binds properties on several activities together. The key overrides issue of MSDN Magazine (msdn.microsoft.com/magazine/cc163504), I in the ActivityToolboxItem base class are CreateComponentsCore built a custom switch activity that was a composite activity with and OnComponentsCreated. multiple child branches. Without a custom toolbox item, when a user dragged my switch Send your questions and comments to mmnet30@microsoft.com. activity from the toolbox to the design surface, the default toolbox Code download available at msdn.microsoft.com/magazine/cc135911. behavior was to simply add an instance of the switch activity. SomeAugust 2008 109 http://msdn.microsoft.com/magazine/cc188697 http://msdn.microsoft.com/magazine/cc188697 http://msdn.microsoft.com/magazine/cc163504 http://msdn.microsoft.com/magazine/cc135911

Table of Contents Feed for the Digital Edition of MSDN Magazine - August 2008

MSDN Magazine - August 2008 Toolbox CLR Inside Out Basic Instincts Cutting Edge Patterns in Practice Data 2.0 - Expose And Consume Data In A Web Services World Biztalk EDI - Build A Robust EDI Solution With BizTalk Server Silverlight - Create Animations With XAML And Expression Blend Write On! - Create Web Apps You Can Draw On With Silverlight 2 Wicked Code - Craft Custom Controls For Silverlight 2 Team System Foundations Windows With C++ Concurrent Affairs Going Places { End Bracket }

MSDN Magazine - August 2008

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