Issue to bind more than one property into single element property

Question

    <Button>
        <Button.Content>
            <MultiBinding StringFormat="{}{0},{1}">
                <Binding Path="Width" RelativeSource="{RelativeSource Mode=FindAncestor,AncestorType={x:Type Window}}"/>
                <Binding Path="Height" RelativeSource="{RelativeSource Mode=FindAncestor,AncestorType={x:Type Window}}"/>                            
            </MultiBinding>
        </Button.Content>
    </Button>

Here i tried to bind the window's width and height into button content but it doesn't make sense.

Answer 1

As Adrian suggested, you have to assign the result of a StringFormat binding to a text control. Try this instead:

  <Button>
    <Button.Content>
        <TextBlock>
            <TextBlock.Text>
                <MultiBinding StringFormat="{}{0},{1}">
                    <Binding Path="ActualWidth" RelativeSource="{RelativeSource Mode=FindAncestor,AncestorType={x:Type Button}}"/>
                    <Binding Path="ActualHeight" RelativeSource="{RelativeSource Mode=FindAncestor,AncestorType={x:Type Button}}"/>                            
                </MultiBinding>
            </TextBlock.Text>
        </TextBlock>
    </Button.Content>
</Button>