WPF: Problem with SelectedItem for ComboBox

Question

XAML:

<ComboBox Height="27" Margin="124,0,30,116" Name="cbProductDefaultVatRate" VerticalAlignment="Bottom" ItemsSource="{Binding}">
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <Label Height="26" Content="{Binding Path=Value}"/>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

Set Data for cbProductDefaultVatRate.Items (Type - VatRate):

private void ShowAllVatRates()
{
    cbProductDefaultVatRate.Items.Clear();
    cbProductDefaultVatRate.ItemsSource = new VatRateRepository().GetAll();
}

Similarly, I defined property:

private Product SelectedProduct
{
    get; set;
}

The Product contains VatRate:

SelectedProduct.DefaultVatRate

How to set SelectedItem equal SelectedProduct.DefaultVatRate? I tried:

cbProductDefaultVatRate.SelectedItem = SelectedProduct.DefaultVatRate;

But it does not work.

Thank you for answers!

Answer 1

Are you looking to get a TwoWay binding like this?

    <ComboBox Height="27" Margin="124,0,30,116" Name="cbProductDefaultVatRate" VerticalAlignment="Bottom" 
ItemsSource="{Binding}" 
SelectedItem="{Binding SelectedProduct.DefaultVatRate, Mode=TwoWay}>
        <ComboBox.ItemTemplate>
            <DataTemplate>
                <Label Height="26" Content="{Binding Path=Value}"/>
            </DataTemplate>
        </ComboBox.ItemTemplate>
    </ComboBox>

Answer 2

You need to make sure that the actual object instance behind SelectedProduct.DefaultVatRate is the same instance as the one that is part of the list returned by new VatRateRepository().GetAll() or object.Equals() must return true for the two instances.