private void ViewReport()
  {
    this.ReportViewer1.ProcessingMode = ProcessingMode.Local;
    this.ReportViewer1.LocalReport.ReportPath = @"Reports/MyReport.rdl";
    this.ReportViewer1.LocalReport.Refresh();

    DataSet ds;
    SqlParameter[] params_ = new SqlParameter[ 3 ];
    params_[ 0 ] = new SqlParameter("Param1", SqlDbType.Int);
    params_[ 0 ].Value = int.Parse(ddlParam1.SelectedItem.Value);
    params_[ 1 ] = new SqlParameter("FromDate", SqlDbType.DateTime);
    try
    {
      params_[ 1 ].Value = DateTime.Parse(tbDateFrom.Text);
    }
    catch
    {
      params_[ 1 ].Value = DateTime.Today.AddYears(- 1 );
    }
    params_[ 2 ] = new SqlParameter("ToDate", SqlDbType.DateTime);
    try
    {
      params_[ 2 ].Value = DateTime.Parse(tbDateTo.Text);
    }
    catch
    {
      params_[ 2 ].Value = DateTime.Today;
    }
    ds = DBUtils.ExecuteProc("MY_REPORT", params_);
    ReportViewer1.LocalReport.DataSources.Clear();
    ReportViewer1.LocalReport.DataSources.Add(new ReportDataSource("MyDataSource", ds.Tables[ 0 ]));

    System.Collections.Generic.List<ReportParameter> params__ = new System.Collections.Generic.List<ReportParameter>();
    params__.Add(new ReportParameter("Param1", ddlParam1.SelectedItem.Value));
    params__.Add(new ReportParameter("FromDate", tbDateFrom.Text));
    params__.Add(new ReportParameter("ToDate", tbDateTo.Text));
    ReportViewer1.LocalReport.SetParameters(params__);
  }

protected void ReportViewer1_Drillthrough(object sender, DrillthroughEventArgs e)
  {
    LocalReport localreport = (LocalReport)e.Report;

    localreport.DataSources.Clear();
    DataSet ds = null;

    localreport.ReportPath = @"Reports/MyReportDD.rdl";

    SqlParameter[] params_ = new SqlParameter[ 1 ];
    params_[ 0 ] = new SqlParameter("Param", SqlDbType.Int);
    params_[ 0 ].Value = int.Parse(e.Report.GetParameters()[ 0 ].Values[ 0 ].ToString());
    ds = DBUtils.ExecuteProc("MY_REPORT_DD", params_);

      localreport.DataSources.Add(new ReportDataSource("MYDataSource", ds.Tables[ 0 ]));

    localreport.Refresh();
  }

if (this.ReportViewer1.LocalReport.IsDrillthroughReport)
      ReportViewer1.PerformBack();