List.Sort in C#: comparer being called with null object

Question

I am getting strange behaviour using the built-in C# List.Sort function with a custom comparer.

For some reason it sometimes calls the comparer class\'s Compare meth

Answer 1

I stumbled across this issue myself, and found that it was related to a NaN property in my input. Here's a minimal test case that should produce the exception:

public class C {

    double v;

    public static void Main() {
        var test =
            new List { new C { v = 0d },
                          new C { v = Double.NaN },
                          new C { v = 1d } };
        test.Sort((d1, d2) => (int)(d1.v - d2.v));
    }

}