Question

I’m in a situation where I need a listbox to remember after postback the attributes I’ve added to a number of the listitems in it. I found this solution online which appears to solve the issue but am not sure how to implement it.

List box solution

He says he wrote a class that inherits from Listbox which is fine, I’ve done that and have called it EnhancedListBox but how do I then apply that to the Listbox I’m using on the page?

I can’t just substitute

<asp:ListBox >

with

<asp:EnhancedListBox>

but how else do I let the page know I want to use my inherited code?

Thanks.

Answer 1

SaveViewState and LoadViewState are virutal methods that you can override. What you want to try is creating “your own” ListBox:

class EnhancedListBox : ListBox
{
    protected override object SaveViewState() 
    {
        // code here from the tutorial
    }
    protected override void LoadViewState(object savedState)
    {
        // code here from the tutorial
    }
}

This is also called “Creating a custom control”, it’s very common to do it this way and it gives you great flexibility.