protected void btnCancelar_Click(object sender, EventArgs e)
 {
     if (txtComentario.Text.Trim() == "")
     {
         UI.Mensaje("Avisos", "Debe especificar un comentario para cancelar el Aviso.", "", Page);
         return;
     }
     using (CobranzasDataContext db = new CobranzasDataContext())
     {
         int idAviso            = Convert.ToInt32(Request["idAviso"]);
         Entidades.Avisos Aviso = db.Avisos.Single(x => x.idAviso == idAviso);
         Aviso.FechaCancelado = DateTime.Now;
         Aviso.Comentario     = txtComentario.Text;
         try
         {
             db.SubmitChanges();
             ScriptManager.RegisterStartupScript(Page, typeof(Page), "ini", "window.parent.CerrarAviso();window.parent.Avisos_Actualizar();", true);
         }
         catch (Exception Ex)
         {
             UI.Mensaje("Avisos", Ex.Message, "", Page);
         }
     }
 }