gridview id using label

protected void finddemoresult()

    {

        string cs = ConfigurationManager.AppSettings["victedudb"];

        cn = new SqlConnection(cs);

        cn.Open();

        string k = "select uname,email,category from demoresult where category='"+dropcategory.Text+"' group by uname,email,category";

        cm = new SqlCommand(k, cn);

        dr = cm.ExecuteReader();

        GridView1.DataSource = dr;

        GridView1.DataBind();

        dr.Close();

        foreach (GridViewRow row1 in GridView1.Rows)

        {

           

            Label lblID = (Label)row1.FindControl("LBLID");

            string k1 = "select sum(marks) from demoresult where email='" + lblID.Text + "'";

            cm = new SqlCommand(k1, cn);

            row1.Cells[4].Text = cm.ExecuteScalar().ToString();

        }

       

    }