This is the way I handled this in the past:
1) assuming the first column is the Int32 'Id number, and the ComboBox ValueMember is bound to 'Id:
DataRow drow = dtbl1.Rows.Cast<DataRow>().First((DataRow row) => row.ItemArray.Equals(4));
datacomboBox.SelectedIndex = (int) drow.ItemArray;
I consider it ugly :), and, today, would look for a better way.
If this is irrelevant to your goal, let me know, and i'll delete this post.