Question

I’m facing a performance issue with a crowded combobox (5000 items). Rendering of the drop down list is really slow (as if it was computing all items before showing any).

Do you have any trick to make this dropdown display lazy?

Xaml code:

  <Grid x:Name="LayoutRoot">
        <StackPanel Orientation="Horizontal" Width="200" Height="20">
            <TextBlock>Test Combo </TextBlock>
            <ComboBox x:Name="fooCombo" Margin="5,0,0,0"></ComboBox>
        </StackPanel>
    </Grid>

code behind:

public MainPage()
{
InitializeComponent();

    List<string> li = new List<string>();

    int Max = 5000;
    for (int i = 0; i < Max; ++i)
        li.Add("Item - " + i);

    fooCombo.ItemsSource = li;
}

Well, there seems to be a bug in the Combobox UI virtualization, so an autocompletebox should be the way to go.

Answer 1

Use the AutoCompleteBox instead, adjust the number of characters that need to be entered before a drop down list will be filled to limit how many drop down items are needed at any one time.