SelectedValue returning an error..

I'll try to be breif with my problem,

I have a database with about 90,000 records. I created a search function which brings the results back in a simple list box.

It displays the data perfect using the DisplayMember property, however I get an error everytime I pass data to SelectedValue (value being the id field which is between 1-90,000). I thought maybe it was a problem with the column but when I pass the same column into the displayMembers (just to test it) it shows up fine.

I really do not know whats wrong, and I have spent hours trying to figure this out (guessing the answer is obvious and right under my nose)

Hopefully someone can help me understand whats going on, or whats not.

Thanks in advance..

PS ...the error being that SelectedValue can not be a null value.

What did you set the ValueMember property to? Is it the fieldname of the value you are trying to set?