protected void btnSave_Click(object sender, EventArgs e)
{
classProvider.AddTimeSlot(
Convert.ToInt32(ddlBranch.SelectedValue),
Convert.ToInt32(ddlDayOfWeek.SelectedValue),
txtTimeStart.Text + "-" + txtTimeEnd.Text);
gvwData.DataBind();
txtTimeStart.Text = String.Empty;
txtTimeEnd.Text = String.Empty;
txtTimeStart.Focus();
}