[RESOLVED] List Box and Mouse Click Event While missing Selected item

[davebold370]

Ok, I have a listbox that has a double click event on it. If you strike the items in the list the program works perfectly without a problem, but if you hit white space, the program blows up.
The frmOpen has a rich text box that uses the data from transfername on it to call forth a name from another system.

The question I have, Is there a way to show the system that there is nothing being clicked? I have tried the selecteditem = 0 and -1 and the selectedindex = 0 and -1 nothing happened. I'm kind of lost on this one. Trying to make this work for my new job.

 Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.MouseDoubleClick
        Dim transfername As String = ListBox1.SelectedItem.ToString()
        frmOpen.Show()
        frmOpen.filename = transfername
    End Sub

VB.net 2010 Professional Edition.

[jmcilhinney]

If no item is selected then what's the value of SelectedItem? Have you actually checked that? What is usually used in VB to represent no object?

[davebold370]

It's referenced as a null object. How do I make a test for that null object with a list box? I'm not to sure how to do that.

Never Mind, I found a try catch. Thanks for the help.

[jmcilhinney]

It's referenced as a null object. How do I make a test for that null object with a list box? I'm not to sure how to do that.

Never Mind, I found a try catch. Thanks for the help.

NOOOOOOOOOO!!! That is a terrible solution. No object in VB is Nothing. All you have to do is test whether the SelectedItem Is Nothing.

[davebold370]

So, Selecteditem = ""

[jmcilhinney]

I'm looking back at my posts and I'm struggling to find where I said that you should compare the SelectedItem to an empty String. I said Nothing and I meant Nothing. You need to do exactly what I said to do:

All you have to do is test whether the SelectedItem Is Nothing.