< asp:GridView ID="GridView1" runat="server"  AllowSorting=true
    onrowcommand="GridView1_RowCommand" 
    onpageindexchanging="GridView1_PageIndexChanging" 
    onsorting="GridView1_Sorting" >
    < PagerSettings FirstPageText="Next" LastPageText="Previous" Mode="NumericFirstLast" 
        NextPageText="Next" PreviousPageText="Previous" />

   <  Columns >                       
     <  asp:BoundField DataField="Type" HeaderText="Project Type"  SortExpression="fprojecttype"/>
    <  asp:BoundField DataField="Priority" HeaderText="Project Priority" SortExpression="fProject_priority_name"
       < asp:BoundField DataField="Start Date" HeaderText="Start Date" SortExpression="START_DATE" />
     <   asp:BoundField DataField="Due  Date" HeaderText="Due  Date" SortExpression="END_DATE"   /> 
              
    

  protected void Page_Load(object sender, EventArgs e)
    {
this.Sortdir = "ASC";
bind();//write fn for bind gridview

}


    private String SortDir
    {
        get { return ViewState["Sortdir"].ToString(); }
        set { ViewState["Sortdir"] = value; }
    }
  

  protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
    {
        if (GridView1.Rows.Count > 1)
        {
            GridView1.DataSource = get_prjects(e.SortExpression, this.Sortdir, Session["CompanyID"].ToString());
            GridView1.DataBind();
            if (this.Sortdir == "ASC")
            {

                this.Sortdir = "DESC";
            }
            else
            {
                this.Sortdir = "ASC";
            }
        }
        else
        {
            fillgrid(str);
        }
    }




 public DataSet get_projects(String strsortfield, String strExpression, string cid)
        {
            DataSet myds = new DataSet();

            try
            {
                String StrQstring = "";
                StrQstring = "select  a,b from tbname  where a. COMPANY_ID=" + cid + "  order by " + strsortfield + " " + strExpression + "";


                getDS(StrQstring, "gprojects");
                if (APMDLStatus)
                {
                    _status = ds;
                    _Status = true;
                }
                else
                {
                    _Status = false;
                }
            }
            catch (Exception ex)
            {
                _projmsg = ex.Message;
                _Status = false;
            }
            return _tstatus;
        }