Why I cannot use HttpResponseMessage class?
问题 I'm new to ASP.NET Web API and want to make HttpResponseMessage instance from a utility class I made. Then I made very simple class. But following compile error occurred. CS0246: The type or namespace name 'HttpResponseMessage' could not be found (are you missing a using directive or an assembly reference?) using System; using System.Collections.Generic; using System.Linq; using System.Net.Http; using System.Web; namespace myapplication.App_Code.Utils { public class HttpUtility { // compile