private Warning[] warnings;
private string[] streamids;
private string mimeType;
private string encoding;
private string extension;
ReportViewer rv = new ReportViewer();
ServerReport sr = rv.ServerReport;
sr.ReportServerUrl = new System.Uri("http://reportserver", System.UriKind.Absolute);

List<ReportParameter> ReportParameters = new List<ReportParameter>();
ReportParameters.Add(new ReportParameter("RP_Date", Form.DateParam.ToString()));
ReportParameters.Add(new ReportParameter("RP_id_Company", "157"));

sr.ReportPath = "/" + ReportName;
sr.SetParameters(ReportParameters);
byte[] bytes = sr.Render(Format, null, out Reports.mimeType, out Reports.encoding, out Reports.extension, out Reports.streamids, out Reports.warnings);
using (System.IO.FileStream FS = new System.IO.FileStream(FileName, System.IO.FileMode.Create))
{
     FS.Write(bytes,  0 , bytes.Length);
     FS.Close();
};

ReportParameters.Add(new ReportParameter("RP_id_Company", "157"));

sr.SetParameters(ReportParameters);

ReportParameters.Add(new ReportParameter("RP_id_Company",  157 ));