Value of type 'Microsoft.TeamFoundation.VersionControl.Client.VersionControlServer' cannot be converted to 'System.Type - vb.net

Question

I'm working on a custom TFS Build workflow based on the code found in two blogs:
http://www.theringworx.com/blog/?p=494
https://lajak.wordpress.com/2011/08/30/tfs2010-retrieve-associated-workitems-to-changesets-tfs-api/
When I implement the VB.Net code within my XAML workflow, I'm currently getting the following errors on build runtime:
The build process failed validation. Details:
Validation Error: The private implementation of activity '1:
DynamicActivity' has the following validation error: Compiler
error(s) encountered processing expression "TFSService".
Value of type
'Microsoft.TeamFoundation.VersionControl.Client.VersionControlServer'
cannot be converted to 'System.Type'.
Validation Error: The private implementation of activity '1:
DynamicActivity' has the following validation error: Compiler
error(s) encountered processing expression "TFS.GetService(Of
VersionControlServer)();".
End of expression expected.
I've traced the error down to this section of code (Simplified from XAML):
TFS=Microsoft.TeamFoundation.Client.TfsTeamProjectCollectionFactory.GetTeamProjectCollectionFactory(New Uri("MyTeamsTFSServer"))
TFSService = TFS.GetService(Of VersionControlServer)()
I've tried changing the type of TFSService from both Microsoft.TeamFoundation.VersionControl.Client.VersionControlServer and System.Type without success.
From what I can tell the error is occurring in the "Of VersionControlServer".
Has anyone ever encountered this? And if so how did you resolve it?

Answer 1

Turns out the issue was the URL I was using, I made a typo when I was entering it in. Yay for descriptive error messages...
I found this while I was checking my authentication using the two methods:
TFS.HasAuthenticated
TFS.Authenticate();
My code blew out when I was running the Authenticate() method.