private void BtnDeleteCategory(object sender, RoutedEventArgs e)
        {
            if (!txtCatId.Text.Equals(""))
            {
                Category c = new Category();
                c.CategoryID = Int32.Parse(txtCatId.Text);
                string msg = da.DeleteCategory(c);
                MessageBox.Show("" + msg);

                if (msg.Equals("Category Discontinued Successful"))
                {
                    MainWindow mw = Application.Current.Windows.OfType <MainWindow>().FirstOrDefault();
                    if (mw != null)
                    {
                        mw.MainFrame.Content = new ManageCategories();
                    }
                }
            }
            else
            {
                MessageBox.Show("Category Id can't be empty");
            }
        }