private void btnFood_Click(object sender, EventArgs e)
{
dtpFrom.Enabled = true;
dtpTo.Enabled = true;
btnFillter.Enabled = true;
chartRevenue.DataSource = BillDAL.GetRevenueByFood();
chartRevenue.Series["Doanh Thu"].ChartType = System.Windows.Forms.DataVisualization.Charting.SeriesChartType.Pie;
chartRevenue.Series["Doanh Thu"].YValueMembers = "Doanh Thu";
chartRevenue.Series["Doanh Thu"].YValueType = System.Windows.Forms.DataVisualization.Charting.ChartValueType.String;
chartRevenue.Series["Doanh Thu"].XValueMember = "Tên Món";
chartRevenue.Series["Doanh Thu"].XValueType = System.Windows.Forms.DataVisualization.Charting.ChartValueType.String;
}