How do I test for <undefined value> in an if statement?

hi

Check if (x == null) -> C#

Prashant

No, already tried that.

hi,

What Error you are getting,also which is the language?
Just post a few lines of code of the function to use this.

Prashant
Prashant

C#

private void listBox1_SelectedIndexChanged(object sender, System.EventArgs e){
collectLink(listBox1.SelectedItem.ToString());
listBox1.Items.Remove(listBox1.SelectedItem);
}

collectLink(listBox1.SelectedItem.ToString()); throws a

An unhandled exception of type 'System.NullReferenceException' occurred in WindowsApplication2.exe Additional information: Object reference not set to an instance of an object.

if(listBox1.SelectedItem.ToString()!=null){
collectLink(listBox1.SelectedItem.ToString());
listBox1.Items.Remove(listBox1.SelectedItem);
}
also throws the same exception.

After stepping through it, I found that it accesses the selectedIndexChange twice. On the second time, it throws the exception at listBox1.SelectedItem.ToString()!=null.

Often on listboxes, you need to check for SelectedItem being null becauase you can have no selected item in a listbox.

if(listBox1.SelectedItem!=null){
  collectLink(listBox1.SelectedItem.ToString());
  listBox1.Items.Remove(listBox1.SelectedItem);
}

-Peter