Binding selected item in ComboBox in WinUI3

Question

I've a ComboBox in WinUI3 with two items manual added:

<ComboBox Width="200" SelectedItem="{Binding MyProp, Mode=TwoWay}">
   <ComboBoxItem Content="1"/>
   <ComboBoxItem Content="2"/>
</ComboBox>

Even if MyProp is set to "1" or "2" initially, the Combobox's text is empty. No item is selected. And if I select one of these items during runtime as user, the value is not written back into MyProp.

But the binding and ViewModel works fine, since a TextBox with the same TwoWay-Binding is working fine in both directions:

<TextBox Text="{Binding MyProp, Mode=TwoWay}"></TextBox>

Do I've to bind the items itself too via a list in the view model? Hoped, to define two ComboboxItem in the XAML is enough.

You should bind to SelectedValue instead since "1" != ComboBoxItem — Eldar
– Eldar, Commented Sep 4, 2023 at 13:54
Nope. Has no effect. If I bind it via SelectedValue, each change of MyProp clears the ComboBox but does not set the correct value. — Konrad
– Konrad, Commented Sep 4, 2023 at 14:19
Yes, you are right That will break in the reverse this time ComboBoxItem != "1". It seems there is no easy way to accomplish this. Either you should use the items source or create a weird value converter that converts between ComboBoxItem string and vice versa. — Eldar
– Eldar, Commented Sep 4, 2023 at 14:26
If you bind to Text and set IsEditable to true, it will work. — Nick
– Nick, Commented Sep 4, 2023 at 14:42

Andrew KeepCoding · Accepted Answer · 2023-09-04 15:06:15Z

4

Since you have ComboBoxItem as items, you need to target the Content property. This should work:

<ComboBox
    SelectedValue="{Binding MyProp, Mode=TwoWay}"
    SelectedValuePath="Content">
    <ComboBoxItem Content="1" />
    <ComboBoxItem Content="2" />
</ComboBox>

But you can avoid using ComboBoxItem explicitly and make it simple:

<ComboBox
    SelectedValue="{Binding MyProp, Mode=TwoWay}">
    <x:String>1</x:String>
    <x:String>2</x:String>
</ComboBox>

answered Sep 4, 2023 at 15:06

Andrew KeepCoding

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