Sending credentials from InvokeWebService activity.

Using Windows Workflow Foundation (WF) to make a call to a web service is pretty straightforward. In most cases, you just drop on the InvokeWebService activity and do some basic configuration.

However, if you are invoking a web service that requires HTTP based authentication before it can be used, you'll need to attach credentials to the outbound request. It took me a while to sort this out, but found its actually pretty easy. You'll know if you need to send credentials because you'll get a HTTP 401: Unauthorized message back if you don't provide them.

The trick is to leverage the InvokeWebServer.Invoking event. Here are the steps:

1. Right click on your invokeWebService activity and click 'Generate Handlers'. This will add two handlers to your code file:


Private Sub invokeWebServiceActivity1_Invoked(ByVal sender As System.Object, ByVal e As System.Workflow.Activities.InvokeWebServiceEventArgs)

End Sub

Private Sub invokeWebServiceActivity1_Invoking(ByVal sender As System.Object, ByVal e As System.Workflow.Activities.InvokeWebServiceEventArgs)

End Sub

2. In the Invoking handler, set your credentials to the WebServiceProxy class.


Private Sub invokeWebServiceActivity1_Invoking(ByVal sender As System.Object, ByVal e As System.Workflow.Activities.InvokeWebServiceEventArgs)
e.WebServiceProxy.Credentials = New System.Net.NetworkCredential("username", "password", "domain")

End Sub


You can also use the NetworkCredential object to impersonate the current user, which would be the user that the Workflow Host is running as.