Setting the SelectedItem for ComboBox component in WPF

Question

I have been defined some ComboBox element:

<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>

and set the data source for component items of VatRate type:

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

VatRate object has a property:

private Product SelectedProduct
{
    get; set;
}

where is a product contains VatRate as well:

SelectedProduct.DefaultVatRate

How to set SelectedItem property of ComboBox to SelectedProduct.DefaultVatRate?

// does not work!!!
cbProductDefaultVatRate.SelectedItem = SelectedProduct.DefaultVatRate;

Thank you for answers!

bitbonk · Accepted Answer · 2010-05-24 18:09:40Z

1

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.

answered May 24, 2010 at 18:09

bitbonk

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1 Comment

akrisanov Over a year ago

Thanks for the tip! While I write as follows: foreach (var item in cbProductDefaultVatRate.Items) { if (Equals(((VatRate)item).Value, SelectedProduct.DefaultVatRate.Value)) cbProductDefaultVatRate.SelectedItem = item; }

Dan Bryant · Accepted Answer · 2010-05-24 18:04:57Z

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>

answered May 24, 2010 at 18:04

Dan Bryant

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1 Comment

bitbonk Over a year ago

SelectedItem is TwoWay bound by default (BindsTwoWayByDefault). So you don't need to explitly redefine that in the xaml binding expression.

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