.net - What's the deal with char.GetNumericValue?

Question

I was working on Project Euler 40, and was a bit bothered that there was no int.Parse(char). Not a big deal, but I did some asking around and someone suggested char.GetNumericValue. GetNumericValue seems like a very odd method to me:

• Takes in a char as a parameter and returns... a double?
• Returns -1.0 if the char is not '0' through '9'

So what's the reasoning behind this method, and what purpose does returning a double serve? I even fired up Reflector and looked at InternalGetNumericValue, but it's just like watching Lost: every answer just leads to another question.

Answer 1

Remember that it's taking a Unicode character and returning a value. '0' through '9' are the standard decimal digits, however there are other Unicode characters that represent numbers, some of which are floating point.

Like this character: ?

Console.WriteLine( char.GetNumericValue( '?' ) );

Outputs 0.25 in the console window.