You can use the windows service by add it in your project as reference, but there is another way to use the web service, by create the class for this service.
You can apply this action by using the wsdl.exe.
how??
C:\Program Files\Microsoft SDKs\Windows\v7.0A\bin>wsdl /out:d:\WebServiceClass.cs
after that, add this class to your project and use the functions of the service.
