gridview delete on selected checkbox

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

        cn = new SqlConnection(cs);

        cn.Open();

        foreach (GridViewRow row1 in GridView1.Rows)

        {

            var chk = (CheckBox)row1.FindControl("ch1");

            if (chk.Checked)

            {

                string k = "delete from demoresult where email=N'" + row1.Cells[2].Text + "' and category=N'" + row1.Cells[3].Text + "'";

                cm = new SqlCommand(k, cn);

                cm.ExecuteNonQuery();

               

            }

        }