WPF data binding

Question

Consider the following XAML code:

    <StackPanel>
        <ListBox x:Name="lbColor">
            <ListBoxItem Content="Blue"/>
            <ListBoxItem Content="Green"/>
            <ListBoxItem Content="Yellow"/>
        </ListBox>
        <TextBlock>
            <TextBlock.Text>
                <Binding ElementName="lbColor" Path="SelectedItem.Content"/>
            </TextBlock.Text>
            <TextBlock.Background>
                <Binding ElementName="lbColor" Path="SelectedItem.Content"/>
            </TextBlock.Background>
        </TextBlock>
    </StackPanel>

I understand how Text property binding works. Internally it is converted to something like:

textBlock.Text = lbColor.SelectedItem.Content;

But how Background is bound to the same source? This code:

textBlock.Background = lbColor.SelectedItem.Content;

is incorrect. How can it work? BTW, it works and shows correct background color.

The only way I see, is to get System.Windows.Media.Colors property with given name, create SolidColorBrush from it and assign to Background property. But there is nothing in the code which points to this path.

Steve Greatrex Steve Greatrex · Accepted Answer · 2010-11-15T11:52:39

This works because there is a built in conversion that allows WPF to convert from a String to a Brush (which is the required type of the Background property).

If you look at the MSDN documentation for Brush, you can see that it is decorated with a TypeConverter attribute that specifies a converter of type BrushConverter.

For general information about type converters, have a read of this article

WPF data binding

1 Answers