SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["ConnectionString"]);
DataSet ds;
protected void Page_Load(object sender, EventArgs e)
{
ds = new DataSet();
SqlDataAdapter da = new SqlDataAdapter("select Table1.Col1,Table2.Col2,Table3.Col3 From Table1,Table2,Table3 where Table1.id=Table2.id and Table2.id=Table3.id", con);
da.Fill(ds);
CrystalDecisions.CrystalReports.Engine.ReportDocument myReportDocument;
myReportDocument = new CrystalDecisions.CrystalReports.Engine.ReportDocument();
myReportdocument.Load(@"MyPathToReportFile.rpt");
myReportdocument.Database.Tables[0].SetDataSource(ds);
CrystalReportViewer1.ReportSource = myReportDocument;
CrystalReportViewer1.DataBind();
}