>>Hi everybody,
>>
>>Ok, another beginner question today.
>>
>>I'm looking at the following code:
>>

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

>>
>>and although I'm not selecting anything in lsbRoles it's going inside this block of code producing the error.
>>
>>I see that the SelectedValue is an empty string in the watch window. So, my first guess was that I need to be able to test for both conditions (empty and null).
>>
>>Googling led me to string.IsEmptyAndNull method, but then I hit this
>>http://msmvps.com/blogs/bill/archive/2006/04/04/89234.aspx
>>
>>So, do you think it's OK to use this method in code or rather use two comparisions instead?
>>
>
>I'd personally use string.IsNullOrEmpty() when I need to check for both conditions. The case you linked to definitely looked like a compiler optimization issue - I've not run into any problems in any of my code.

Thanks, Paul, going to experiment with yours and Greg suggestions.