The service contract file is an interface that has WCF service attributes applied. Service contract file (IService1.cs or IService1.vb). When you create a new project using the WCF Service template, the new project automatically includes the following three files: The WCF Service Library project template is available in the new project dialog box under Visual C#\WCF and Visual Basic\WCF. You can use these templates to create a simple service with minimal code interaction, as well as a building block for more advanced services. Specifically, these templates provide the basic definitions for service contract, data contract, service implementation, and configuration. WCF Visual Studio templates provide a basic class structure for service development. Windows Communication Foundation (WCF) Visual Studio templates are predefined project and item templates you can use in Visual Studio to quickly build WCF services and surrounding applications.