<GridViewColumn Width="120"
                ap:ColumnSort.PropertyName="{Binding Salary}"
                DisplayMemberBinding="{Binding Salary, Converter={StaticResource CurrencyConverter}}"
                Header="{t:Translate Salary}" />

public static class ColumnSort
{
    public static readonly DependencyProperty PropertyNameProperty = DependencyProperty.Register("PropertyName", typeof(BindingExpression), typeof(ColumnSort));

    public static BindingExpression GetPropertyName(DependencyObject target) => (BindingExpression)target.GetValue(PropertyNameProperty);

    public static void SetPropertyName(DependencyObject target, BindingExpression value) => target.SetValue(PropertyNameProperty, value);
}

public int Compare(object x, object y)
{
    var xValue = GetPropertyValue(x);
    var yValue = GetPropertyValue(y);

    if (_sortOrder == SortOrder.Ascending)
        return Comparer.Default.Compare(xValue, yValue);

    return Comparer.Default.Compare(yValue, xValue);
}

private object GetPropertyValue(object item)
{
    if (item == null)
        return null;

    var dependencyObject = new UIElement();

    var binding = CreateBinding(item, _bindingExpression); // Create a new Binding from the BindingExpression

    BindingOperations.SetBinding(dependencyObject , DummyProperty, binding);

    return _dependencyObject.GetValue(DummyProperty);
}