c# - Crystal report viewer triggers invalid cast exception error -

i using crystal reports ver 14 visual studio 2010/12. continue have problem crystal reports view triggers following: system.invalidcastexception error. when trying set viewer report source.

-running windows os7 latest updates -report has data -report prints directly printer fine

     ////////////////// create report document//////////////////////////////       reportdocument crreport = new reportdocument();      // load .rpt file; statement need changed reference       application.startuppath       crreport.load(@"c:\cpms.net.sql\cpms.net\crpprojectlist.rpt");      // set report title1, title2, title3 here       // txttitle1      // txttitle2      // txttitle3       // set report datasource ds.tables[2]; tables[2] = tbl01_general      crreport.setdatasource(ds);       // set viewer control , preview report      this.axcrystalactivexreportviewer1.begininit();      this.axcrystalactivexreportviewer1.reportsource = crreport; //this line causing problem      this.axcrystalactivexreportviewer1.refresh(); 

code requested commenter:

    try      {    ///////////////////// create ado.net dataset connect report object /////////////////  // initialize connection object, connection string, , sql string  sqlconnection cnn;  string connectionstring = null;  string sql = null;  // set connection string server , database , sql string   connectionstring = @"data source=vteglasi-think\mssqlexp12;initial catalog=cpms_sql;integrated security=true";   cnn = new sqlconnection(connectionstring);  // sql = "select pin, route, worktype, proj_cat, respagency, cont_cost, let_date tbl01_general worktype = '3r'"; // test sql   sql = "select [tbl01_general].pin, [tbl01_general].route, [tbl01_general].worktype, [tbl01_general].proj_cat, [tbl01_general].respagency, [tbl01_general].cont_cost, [tbl01_general].let_date, [tbl01_selected].selected tbl01_general, tbl01_selected [tbl01_selected].selected = 1"; // test sql  // set sqldataadapter craete data set ds, become data source crreport object  sqldataadapter adaptercpms_net = new sqldataadapter(sql,cnn);