Hi,
Please review the following:
this.reportViewer.ProcessingMode = Microsoft.Reporting.WebForms.ProcessingMode.Local;
this.reportViewer.LocalReport.ReportPath = Server.MapPath("//Path to your report");
this.reportViewer.LocalReport.DataSources.Clear();
this.reportViewer.LocalReport.DataSources.Add(new Microsoft.Reporting.WebForms.ReportDataSource("Data Set Name", DataSet Variable));
Microsoft.Reporting.WebForms.ReportParameter[] parameters = new Microsoft.Reporting.WebForms.ReportParameter[1];
parameters[0] = new Microsoft.Reporting.WebForms.ReportParameter("Param Name", Par. Value, true);
this.reportViewer.LocalReport.SetParameters(parameters);
this.reportViewer.LocalReport.Refresh();
Hope this helps.>!!
Nayan