WPF DataGrid CustomSort for each Column

Question

I have a WPF DataGrid bound to a CollectionViewSource that encapsulates an ObservableCollection. This CollectionViewSource has two main objectives:

1) To group each

Answer 1

The answer given by trilson86 is excellent. However, the third parameter in the two DependencyProperty declarations is incorrect. Instead of DataGrid and DataGridColumn, they should be CustomSortBehaviour, as such:

public static readonly DependencyProperty AllowCustomSortProperty =
        DependencyProperty.RegisterAttached("AllowCustomSort", 
        typeof(bool),
        typeof(CustomSortBehaviour), // <- Here
        new UIPropertyMetadata(false, OnAllowCustomSortChanged));

    public static readonly DependencyProperty CustomSorterProperty =
        DependencyProperty.RegisterAttached("CustomSorter", 
        typeof(ICustomSorter), 
        typeof(CustomSortBehaviour));  // <- Here

I kept getting a warning that the AllowCustomSort property was already registered. A little research led me to the answer here.

At any rate, it's an excellent answer, so thank you.