2 Properties in One Binding?

Question

Can I combine 2 elements in one biding?

<Canvas>
    <Ellipse Fill="Black" x:Name="dot1" Width="16" Height="16" Canvas.Left="124" Canvas.Top="133"/>
    <Ellipse Fill="Black" x:Name="dot2" Width="16" Height="16" Canvas.Left="221" Canvas.Top="40"/>
    <Line Stroke="Black" x:Name="line1" 
          X1="{Binding ElementName=dot1, Path=(Canvas.Left)}" 
          Y1="{Binding ElementName=dot1, Path=(Canvas.Top)}"

          X2="{Binding ElementName=dot2, Path=(Canvas.Left)}" 
          Y2="{Binding ElementName=dot2, Path=(Canvas.Top)}"
          />
</Canvas>

I need not only to bind the Line Start and End Points to the dots Left and Right, but the addition of (Left + Width / 2) and (Top + Height / 2) (centers).

Is that possible?

Answer 1

Yes, use a MultiBinding and implement the formula in a IMultiValueConverter.

Edit:

Something like this where only X1 uses the MultiBindingand the rest are unchanged.

<Canvas>
    <Ellipse Fill="Black" x:Name="dot1" Width="16" Height="16" Canvas.Left="124" Canvas.Top="133"/>
    <Ellipse Fill="Black" x:Name="dot2" Width="16" Height="16" Canvas.Left="221" Canvas.Top="40"/>
    <Line Stroke="Black" x:Name="line1" 
    Y1="{Binding ElementName=dot1, Path=(Canvas.Top)}"

    X2="{Binding ElementName=dot2, Path=(Canvas.Left)}" 
    Y2="{Binding ElementName=dot2, Path=(Canvas.Top)}">
        <Line.X1>
            <MultiBinding Converter="{StaticResource myMultiValueConverter}">
                <Binding Path="(Canvas.Top)"/>
                <Binding Path="(Canvas.Left)"/>
            </MultiBinding>
        </Line.X1>
    </Line>
</Canvas>

Answer 2

You can bind to multiple properties using a MultiBinding.

There are several examples and tutorials on this out there - e.g. this and this seems to tell you what you need to know.