How to access GetGlobalResourceObject()

I'm new to c#. I have this class开发者_如何学运维...

using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;


public class clsErrorMessages
{
    string _sErrors;
    public clsErrorMessages(string sErrorTextFileName)
    {
        _sErrors = (String)GetGlobalResourceObject("resource","FriendlyErrors.txt");

    }
}

The compiler says the name 'GetGlobalResourceObject' does not exist in the current context

Do I need to include another using?

The GetGlobalResourceObject() method is a static member of the HttpContext class. You need to qualify it as such:

_sErrors = (string) HttpContext.GetGlobalResourceObject("resource",
    "FriendlyErrors.txt");