MS Access Search Form need to pass values from unbound combo box to query

问题

I have a very simple table with about 10 columns. I have set up a search form with all unbound fields and a couple of combo boxes that reference the table on 2 columns, one for each combo box. I have been using this for these two types of criteria in my query:

1) Like "*" & [Forms]![Contract Search]![ContractName] & "*"

2) Like IIf(IsNull([Forms]![Contract Search]![Amount]),"*",[Forms]![Contract Search]![Amount])

Basically i have the first one setup to match anything in the text box and if left blank return all. The second one I have setup to match exact or if null return all. I want to use the second criteria logic for the combo boxes.

This works fine for the text boxes and check boxes but when I use the same format for the combo box it doesn't display anything on the query.

Combo Box Criteria I am using:

IIf(IsNull([Forms]![Contract Search]![Project]),"*",[Forms]![Contract Search]![Project])

even a simple criteria:[Forms]![Contract Search]![Project] does not work with the combobox.. if i convert it to a text box it works..

The values show up fine in the combo box in the search form, but they dont seem to pass the selection to the query. I dont understand what I am doing wrong. These are all unbound controls. I am using Microsoft Access 2010.

来源：https://stackoverflow.com/questions/25120980/ms-access-search-form-need-to-pass-values-from-unbound-combo-box-to-query