public void bindgrd()
    {
        SqlConnection conn = new SqlConnection();

        conn.ConnectionString = ConfigurationManager.ConnectionStrings     ["cn"].ConnectionString.ToString();

            conn.Open();

            Q = "select * from tablename";   

            adp = new SqlDataAdapter(Q, conn);

            ds = new DataSet(); 

            adp.Fill(ds, "tablename");

            Gridview1.DataSource = ds.Tables["tablename"];

            Gridview1.DataBind();
           
           
   }

protected void Gridview1_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        Gridview1.PageIndex = e.NewPageIndex;

        bindgrd();

    }