Sorting the gridview column wise, using datasource

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

/// <summary>
/// Summary description for AutowithholdruleforDS
/// </summary>
public class AutowithholdruleforDS
{
    public AutowithholdruleforDS()
    {
        string Cachekey = "AutowithholdRule_" + HttpContext.Current.Session.SessionID;
         this.CD1 = (DataTable)HttpRuntime.Cache[Cachekey];
    }
    private DataTable CD1;

    public DataView Select()
    {
        if (this.CD1 != null)
        {
            this.CD1.DefaultView.Sort = "";
            return this.CD1.DefaultView;
        }
        else
        {
            return null;
        }
    }
}