Question

<StackPanel Name="mypanel">
   <ScrollViewer Height="{Binding ElementName=mypanel, Path=ActualHeight}">

I need, Height = mypanel.ActualHeight-60.

How can I do it?

EDIT:

<StackPanel Name="mypanel">
    <ContentControl Content="{Binding HeaderPart}" /> <= here must be Expander
    <ScrollViewer Height="{Binding ElementName=mypanel, Path=ActualHeight, Converter={StaticResource HeightConverter}}" >
        <StackPanel>
        </StackPanel>
    </ScrollViewer>

When there is no Expander, all is working. When the Expander is, mypanel.ActualHeight, HeightAdjustmentConverter = 0.

What happened?

Answer 1

You need to write an IValueConverter that takes in the ActualHeight and returns a new value of that minus 60.

Something like:

[ValueConversion(typeof(double), typeof(double))]
public class HeightAdjustmentConverter: IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        double original = (double)value;
        return double - 60;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        double adjusted = (double)value;
        return adjusted + 60;
    }
}