private void btnGenerar_Click(object sender, EventArgs e)
{
DateTime ini = Convert.ToDateTime(txtFechaInicio.Text);
DateTime fin = Convert.ToDateTime(txtFechaFin.Text);
List <Ventas> detalles = VentasBLL.GetVentasBetweenDates(ini, fin);
ReportDataSource dt = new ReportDataSource("VentasPeriodos", detalles);
ReportParameter pYear = new ReportParameter("dtInicio", txtFechaInicio.Text);
ReportParameter pMonth = new ReportParameter("dtFin", txtFechaFin.Text);
this.reportViewer1.LocalReport.SetParameters(new ReportParameter[] { pYear });
this.reportViewer1.LocalReport.SetParameters(new ReportParameter[] { pMonth });
this.reportViewer1.LocalReport.DataSources.Clear();
this.reportViewer1.LocalReport.DataSources.Add(dt);
this.reportViewer1.RefreshReport();
}