定义服务契约

定义服务契约IEmployeeService，对外提供服务操作功能，以对应REST服务的CURD操作：

• IEnumerable GetAllEmployees() 获取所有的员工对象
• Employee GetEmployeeById(string id) 由id获取指定的员工
• void AddEmployee(Employee employee) 增加一个员工对象
• void UpdateEmployee(Employee employee) 更改一个员工对象信息
• void DeleteEmployee(string id) 删除id指定的员工

Restful WCF的服务契约定义例子代码如下：

[ServiceContract]
public interface IEmployeeService
{
    [OperationContract]
    [WebGet(UriTemplate = "employee/{id}", RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)]
    Employee GetEmployeeById(string id);  

    [OperationContract]
    [WebGet(UriTemplate = "employees", RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)]
    IEnumerable<Employee> GetAllEmployees();

    [OperationContract]
    [WebInvoke(Method = "POST", UriTemplate = "employee", RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)]
    void AddEmployee(Employee employee);

    [OperationContract]
    [WebInvoke(Method = "PUT", UriTemplate = "employee", RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)]
    void UpdateEmployee(Employee employee);

    [OperationContract]
    [WebInvoke(Method = "DELETE", UriTemplate = "employee/{id}", RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)]
    void DeleteEmployee(string id);  

}

代码中通过[ServiceContract]和[OperationContract]两个Attribute来标记接口类和方法，来告诉编译器这是服务契约和操作契约。