void display()
    {
        DataTable dt = dm.DisplayAllQuestions();

        GVFirst.DataSource = dt;
        GVFirst.DataBind();
    }
 protected void GVFirst_PageIndexChanging(object sender, GridViewPageEventArgs e)
 {
     display();
     GVFirst.PageIndex = e.NewPageIndex;
     GVFirst.DataBind();
 }