protected void btnSave_Click(object sender, EventArgs e)
 {
     try
     {
         classProvider.AddSchedule(
             Convert.ToInt32(ddlDayOfWeek.SelectedValue),
             Convert.ToInt32(ddlBranch.SelectedValue),
             Convert.ToInt32(ddlYear.SelectedValue),
             Convert.ToInt32(ddlMonth.SelectedValue),
             Convert.ToInt32(ddlClass.SelectedValue),
             ddlLevel.SelectedValue,
             Convert.ToInt32(ddlClassRoom.SelectedValue),
             ddlTimeStart.SelectedItem.Text.Split('-')[0],
             ddlTimeStart.SelectedItem.Text.Split('-')[1],
             Convert.ToInt32(ddlInstructor.SelectedValue));
         gvwDetail.DataBind();
         ddlTimeStart.SelectedIndex = 0;
     }
     catch (Exception ex)
     {
         ScriptManager.RegisterStartupScript(this, this.GetType(), "_error", "alert('" + ex.Message + "')", true);
     }
 }