Speeding up listbox insertion time

I need to add 950 strings that are 2500 characters in length to a listbox. The method I am u开发者_如何学Csing below takes 2.5 seconds and ideally it needs to happen in less then 500ms.

Stopwatch sw = Stopwatch.StartNew();

listBox1.BeginUpdate();
listBox1.Items.AddRange(items.ToArray());
listBox1.EndUpdate();

sw.Stop();

What would be the best way to optimize the insertion time?

Thanks.

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One thing you could try is changing this line:

listBox1.Items.AddRange(items.ToArray());

to something like this:

foreach (var item in items)
{
    listBox1.Items.Add(item);
}

That way, you do not have the overhead of creating a whole new array (the ToArray() call) before putting the items into your ListBox.

---

Listbox is dealing with 2500 characters. That is what is slow. All that data, including converting to/from arrays, is peanuts in memory. Hence skipping the ToArray step not making a difference. If your users have to scroll horizontally to see this info, chances are, you're stuck with 'slow.'

If not, consider refactoring a tiny bit. Strategy: only put as many characters - about 100 - as are viewable in a regular width listbox. Full strings are retained behind the scenes.

• Make a helper class like so (you can convert the public string to a property if you're that anal;-):

    Class TruncatedListItem
        Public Content as string
        Overrides sub ToString() as string ' Pardon me if this is wrong I always use intellisense
            return Mid(Content,1,100)
        end sub
    end class

• Add those items to the listbox. When an item in a listbox isn't of type string, it calls the item's ToString method (which hey, we just tailored to give the listbox a break) and adds that as a string, then the items collection appears as the items you've added. (keep the begin/end update too)

  For each each itm as string in Items
      dim tli as new TruncatedListItem
      tli.Content = itm
      listbox.add(tli)
  next
  

• When you want to see what the user picked, instead of getting the string like this:

  MyString = Ctype(Listbox.SelectedItem,string)  

• do this MyString = Ctype(ListBox.SelectedItem,TruncatedListItem).Content
• Now I am assumming the user, at some point, still needs to see all 2500 chars before selecting. Unless they are a serious stick in the mud, they should settle for this alternative (In fact there are advantages to scrolling).
  • When they double click an item, in the handler for double click, show them the full text in a messagebox. You could tell them to do that in a tooltip. For example, in the double-click handler: msgbox Ctype(ListBox.SelectedItem,TruncatedListItem).Content,,"Full Item Text"

Good luck!