>Would you not better use and AND instead of an OR ?
>
>>

>> if ((this.lsbUsers.SelectedItem != null &&  this.lsbUsers.Text != string.Empty)
>>            && this.LsbRoles.SelectedValue != null)

>
>I think the best thing to do is to always test for null first

I think you're right here, that when we need to test for negatives we need to use AND instead of OR.

I'll try that first and see, if it would resolve the problem.

If not, I appreciate future comments on the exact method in question.

UPDATE. Nope, no cigar.