In these days we're observing lots of curiosity and interesting around the Workflow capabilites in Sharepoint and during our demos I'm trying to show to my customers that you don't need to be an expert on Windows Workflow Foundation in order to create the biggest part of the workflows that your business needs.
If you decide to adopt the Sharepoint platform, you've a powerful and adaptable workflow platform and you've a tool that can really tune up your business: Sharepoint Designer.
Sharepoint Designer has an intuitive wizard that permits you to build, compile and install a workflow on a Sharepoint library in few minutes. With the standard activites exposed by Sharepoint Designer you can build really a big amount of different workflows and I love to show that, only with the standard features and a careful Sharepoint Site design, you can satisfy a big amount of your business needs.
But Sharepoint Designer is more than this... what many people doesn't know is that Sharepoint Designer is extendible: if you're a developer, you can create custom workflow activities with Visual Studio and Windows Workflow Foundation and make them available to use with Sharepoint Designer in a simple and intuitive manner to your end users.
The steps in order to make a workflow activity available to Sharepoint Designer are essentially these:
- Create the custom activity with Visual Studio
- Register the Workflow Activity dll in the GAC on the SharePoint server
- Register the Workflow Activity dll in the <authorizedTypes> section of the web.config on the SharePoint server (remember that if your site is running on a specific port (for example 111) the we.config to update is located on C:\Inetpub\wwwroot\wss\VirtualDirectories\111\web.config).
- Register the activity for use in SharePoint Designer via the WSS.ACTIONS file on the SharePoint server
You can find an interesting tutorial here.
With these extensions, Sharepoint Designer can become really an interesting workflow editor I think and, more important, available to users that are not developers or that doesn't have development knowledges.
If you're interested on custom activities for Sharepoint Designer, remember that on CodePlex there's an interesting project called Useful Sharepoint Designer Custom Workflow Activities with interesting ready to run objects. My favourite? The Start Another Workflow activity (a lack on Sharepoint Designer I think... 
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