set datasource

How to set datasource after merging two tables for crystal report in c#,vs2008,sql2008

ReportDocument rd = new ReportDocument();

rd.Load("C:\\REPORTS\\crystalReport8.rpt");

//rd.Load("H:\\MANEESH\\PROJECT\\13-08-2014\\LAB SOFTWARE\\crystalReport4.rpt");

//rd.Load("E:\\MY PROJECT\\19-08-2014\\LAB SOFTWARE\\crystalReport4.rpt");

//rd.SetDataSource(ds.Tables[0]);

//rd.SetDataSource(dss.Tables[0]);

DataSet ds3 = new DataSet();

ds3.Merge(ds);

ds3.Merge(dss);

rd.SetDataSource(ds3.Tables[0]);

crystalReportViewer8.ReportSource = rd;