the type or namespace webget could not be found

In "project properties" make sure your "target framework" is set to : .NET Framework 4

and not: .NET Framework 4 Client Profile, or any lower .NET version.

You need to reference the System.ServiceModel.Web DLL.

Right-click the 'References' folder in your project and choose 'Add Reference...'. Scroll down 

to System.ServiceModel.Web and click 'OK'.