tags:

views:

157

answers:

2
+1  Q: 

How can I allow a blank value on a lookup field in a TDBGrid?

I have a column in my dbgrid that is based on a lookup field.

The problem is that the end user can't set a blank value for the field - they can only select values from the lookup table.

How can I allow the end user to delete or 'blank out' a value for the column?

A: 

Try putting a blank value in the lookup table.

Mason Wheeler  2009-09-30 18:47:07
I thought of that - surely there's a way to do this without adding extra data...?
croceldon  2009-09-30 18:48:10
Not that I know of. The point of a lookup is to give you choices based on a list defined somewhere else. If you start adding options that aren't on that list then you no longer have a lookup.
Mason Wheeler  2009-09-30 19:19:01
+2  A: 

In the appropriate TDBGrid Key event, trap for DEL. When detected, check to see if you're in the lookup column. If so, call Clear on corresponding dataset field.

Larry Lustig  2009-09-30 19:37:01
How can I tell if I'm in the lookup column?
croceldon  2009-09-30 20:15:09
Read DBGrid.SelectedIndex or, even better, DBGrid.SelectedField which will give you the field object to Clear() directly.
Larry Lustig  2009-09-30 21:03:36
Well, that's really close. I'm calling something like grid.SelectedField.Clear, but it doesn't seem to work. The field is unaffected in the grid.
croceldon  2009-10-01 14:46:05
Ok, here's what I came up with that works: with grid.DataSource.Dataset do begin Edit; FieldByName('fieldname').Clear; Post; end;Probably a better way of doing it, but that works. Thanks!
croceldon  2009-10-01 15:02:20
Glad I was able to get you close, even if not all the way. Not sure I've done this in a grid before, but I have with DBComboBox set to DropDownList style — same idea, but easier to get back to the appropriate field object.
Larry Lustig  2009-10-01 15:16:19

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