Question

I have a List<T> where T is a class that exposes a “Username” property. Username is of a custom type that encapsulates a string. I implemented the IComparable<T> interface on this custom type that simply returns

this.encapsulatedString.CompareTo(other.encapsulatedString)

I defined an ICollectionView of the List thus:

AllUsers=CollectionViewSource.GetDefaultView(myList);

I added a Sortdescription:

AllUsers.SortDescriptions.Add(new SortDescription("Username",ListSortDirection.Ascending));

On this line the code throws the exception stated in the title. I can sort the list by other means without problem. Where is the exception coming from?

Answer 1

The custom type has to implement IComparable as well as IComparable<T>. It seems the SortDescription uses the old fashioned non-generic version of CompareTo.