Correct Use of .NET Exception

Question

What is the correct exception to throw in the following instance?

If, for example, I have a class: Album with a collection of Songs:

List<Song>

And a method within Album to add a Song:

public void AddSong(Song song)
{
    songs.Add(song);
}

Should I throw an exception if a user attempts to add a song that already exists? If so, what type of exception?

I have heard the phrase: "Only use exceptions in exceptional circumstances", but I want to tell the client implementing Album exactly what has gone wrong (not just return a Boolean value).

Answer 1

In exactly the same situation, the .NET designers at Microsoft chose to throw ArgumentException with a descriptive message. Oh, and they were pretty consistent about that.