ComboBox - MaxDropDownHeight seems to be limited to 15 items - WinUI 3

Question

I would like to have the ComboBox's dropdown as long as it gets depending on the available space on the screen that the user has less scrolling; faster access.

I've tested it:

• If i have the ComboBoxItems tags in the xaml code directly and i set the MaxDropDownHeight to for i.e. 10000, it shows one more item, 15.
• If i generate the CombobBoxItems by ViewModel and a template, it shows 2 more items, 15.

So the dropdown is in general 1 item shorter generated by a template.

• I've also set MaxDropDownHeight in the app.xaml from the generic.xaml, this has the same behaviour.
• I've tried to set the OpenedLength of the dropdown in the app.xaml but that defines only the drawing.

I can't find any infos about it, is this the restriction?

Windows.UI.Xaml.Controls.ComboBox.MaxDropDownHeight

ADDENDUM:

There is no Auto option.

Answer 1

Hello,

Welcome to Microsoft Q&A!

This is not a bug.

In ComboBox resource , ComboBox is designed to display a maximum of 15 item.

<x:Int32 x:Key="ComboBoxPopupMaxNumberOfItems">15</x:Int32> 

If you want to change the max number of items, you can override ComboBoxPopupMaxNumberOfItems in App.xmal, and set the appropriate MaxDropDownHeight in ComboBox.

<Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
                <!-- Other merged dictionaries here -->
            </ResourceDictionary.MergedDictionaries>
            <!-- Other app resources here -->
            <x:Int32 x:Key="ComboBoxPopupMaxNumberOfItems">20</x:Int32>
        </ResourceDictionary>
</Application.Resources>

Thank you.

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