Try this
public ReportDocument rpt = new ReportDocument();
protected void Page_Load(object sender, EventArgs e)
{
rpt.FileName = "C:\\Users\\rasmikantm\\Desktop\\aaa\\CrystalReport.rpt";
rpt.Load("C:\\Users\\rasmikantm\\Desktop\\aaa\\CrystalReport.rpt");
CrystalReportSource1.ReportSource = rpt;
}
"CrystalReportSource1" is your CrystalReportViewerID .