Question

I’ve got a Windows Forms application with two ListBox controls on the same form. They both have their SelectionMode set to ‘MultiExtended’.

When I change the selection of one the selection of the other changes.

Now I thought I’d done something stupid with my SelectedIndexChanged handlers so I removed them and re-wrote them from scratch, and got the problem.

So I created a brand new WinForms app and dragged two ListBoxes onto the forms surface.

In the constructor I populated them both with the following.

List<Thing> data = new List<Thing>();  for ( int i = 0; i < 50; i++ ) {         Thing temp = new Thing();         temp.Letters = 'abc ' + i.ToString();         temp.Id = i;         data.Add(temp); }  listBox1.DataSource = data; listBox1.DisplayMember = 'Letters'; listBox1.ValueMember = 'Id';   List<Thing> data2 = new List<Thing>();  for ( int i = 0; i < 50; i++ ) {     Thing temp = new Thing();     temp.Letters = 'abc ' + i.ToString();     temp.Id = i;     data2.Add(temp); }  listBox2.DataSource = data2; listBox2.DisplayMember = 'Letters'; listBox2.ValueMember = 'Id'; 

And then I built and ran the app.

Started selecting some values to see if the symptoms were present. And they were!

This is literally all the code I added to the form,I had not added any event handlers, I have tried it with the SelectionMode set to ‘One’ and ‘MultiExtended’.

Can anyone give me a clue as to why this is happening.

Cheers

Answer 1

It isn’t the list that stores the current position – it is the CurrencyManager. Any controls (with the same BindingContext) with the same reference as a DataSource will share a CurrencyManager. By using different list instances you get different CurrencyManager instances, and thus separate position.

You could achieve the same simply by using .ToList(), or creating a new List<T> with the same contents (as per your original post), or by assigning a new BindingContext to one of the controls:

control.BindingContext = new BindingContext();