Change the definitions:
DBOprX dbOpr = new DBOprX();
BindingSource bs = new BindingSource(new System.ComponentModel.Container());
DataSet ds = new DataSet();
to:
DBOprX dbOpr;
BindingSource bs;
DataSet ds;
Change the GetData()
void GetData()
{
dbOpr = new DBOprX();
bs = new BindingSource(new System.ComponentModel.Container());
ds = new DataSet();
ds = dbOpr.SelectMSSQLQry("Select * FROM Stu", "Students");
bs.DataMember = "Students";
bs.DataSource = ds;
cboStudents.DataSource = bs;
cboStudents.DisplayMember = "Name";
cboStudents.ValueMember = "Id";
cboStudents.SelectedIndex = -1;
}