Strange listbox datasource behaviour

Andre Hendriks

Hi,

When I set the DataSource property for two listboxes to the same list (List) and I select an item in one listbox, this is automatically selected in the second listbox too. That is pretty weird behaviour in my opinion. Has anyone seen that before? Is it a know bug in Visual Studio Professional 2012 (11.0.61030.00 update 4) / .NET framework 4.5.50709 ?

Thanx,

André

example code (in form with two listboxes, MyClass just some class):

List classes = new List(10);
for (int k = 1; k < 6; k++)
{
MyClass d = new MyClass(k.ToString(), String.Format("name-{0}", k));
classes.Add(d);
}
listBox1.DataSource = classes;
listBox2.DataSource = classes;

3 Replies

Know the answer? Post it — somebody with the same question will find it here.

Andre Hendriks11y ago
Well, consensus seems to be that the property of being selected is more connected to the list than to the listbox. Not my logic, but I will insert a separate bindingsource... André
Tom Mohan11y ago
I believe this is not a bug. You are assigning same list class to two different list boxes. But the class is reference type. so the two listbox's datasource pointing to same memory location.
Vulpes11y ago
That in fact is normal behavior when the DataSource is the same object.

If you want the listboxes to behave independently, then I'd wrap your list in different BindingSource objects:

List classes = new List(10);
for (int k = 1; k < 6; k++)
{
MyClass d = new MyClass(k.ToString(), String.Format("name-{0}", k));
classes.Add(d);
}
BindingSource bs1 = new BindingSource();
BindingSource bs2 = new BindingSource();
bs1.DataSource = classes;
bs2.DataSource = classes;
listBox1.DataSource = bs1;
listBox2.DataSource = bs2;