Try catch error

Hello:
I have text box get data from dataread. Here my code:
OleDbCommand com = new OleDbCommand("select sid from TableOne where pid = " + "'" + PID.SelectedValue + "'" + " and gid = " + "'" + GID.SelectedValue + "'" + " and unitid = " + "'" + tid.SelectedValue + "'");
        ....
        ........

        Txtsid.Text = myDataReader[0].ToString().Trim();
I got the run time error at line: Txtsid.Text = myDataReader[0].ToString().Trim();
Invalidoperationexception was unhandled by user code
No data exists for the row/column
 How to try catching those errors?
 As always, your help is highly appreciated!
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