Question

This code:

        Console.WriteLine("~".CompareTo("a") > 0);
        Console.WriteLine('~'.CompareTo('a') > 0);

Gives me:

False
True

WTF?

Answer 1

Another way to show this behaviour is:

Console.WriteLine("a".CompareTo("b")); // -1 
Console.WriteLine("b".CompareTo("a")); // 1
Console.WriteLine('a'.CompareTo('b')); // -1 
Console.WriteLine('b'.CompareTo('a')); // 1

Console.WriteLine("~".CompareTo("a")); // -1
Console.WriteLine("a".CompareTo("~")); // 1
Console.WriteLine('~'.CompareTo('a')); // 29
Console.WriteLine('a'.CompareTo('~')); // -29

The difference may be subtle, but it is documented. The comparison in Char.CompareTo(Char) is

based on
the encoded values of this instance
and value, not their lexicographical
characteristics.

At the same time, the documentation for String.CompareTo(String)

performs a word (case-sensitive and
culture-sensitive) comparison using
the current culture.

I.e. the first one bases the comparison on order, the latter on the default rules in the current culture (the order you might see in a dictionary).