Can't find [WebInvoke] and [WebGet]

Need to add the reference System.ServiceModel.Web.dll and import the namespace System.ServiceModel.Web by using below statement using System.ServiceModel.Web; Then it will work.

[WebInvoke(BodyStyle = WebMessageBodyStyle.WrappedRequest, RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)]

[OperationContract]

[WebInvoke(Method = "POST", UriTemplate = "/Save")]