کد رو به این شکل تغییر دادم و درست شد :
universityDataSet dataset = new universityDataSet();
rwd.adapt = new SqlDataAdapter("", rwd.connection);
rwd.adapt.SelectCommand.CommandText = "select * from student";
rwd.adapt.Fill(dataset, "student");
rwd.adapt.SelectCommand.CommandText = "select * from karnameha";
rwd.adapt.Fill(dataset, "karnameha");
rwd.adapt.SelectCommand.CommandText = "select * from previewforkarname";
rwd.adapt.Fill(dataset, "previewforkarname");
repname.SetDataSource(dataset);
crystalReportViewer1.ReportSource = repname;