cant find TetxBox from selectIndexChanged in listview

protected void ListView1_SelectedIndexChanged(object sender, EventArgs e)

{

TextBox btnModify = (TextBox)items.FindControl("TextBoxL");

SqlConnection c = new SqlConnection(ConfigurationManager.ConnectionStrings["ApplicationServices"].ConnectionString);

int myindex = ListView1.SelectedIndex;

string myId = ListView1.DataKeys[myindex][0].ToString();

//testing the value returned correctly

Response.Write(myId);

SqlCommand cmd = new SqlCommand("insert into rply(task_id,comment,rply_name,rpl_date)values('" + myId + "','" + btnModify.Text + "','" + s2 + "','" + DateTime.Now.ToString("MM/dd/yyyy HH:mm:ss") + "')", c);

c.Open();

cmd.ExecuteNonQuery();

c.Close();

}