1000000000 * 3 = -1294967296?

Question

I'm confused!

Today is November 3rd

DateTime DateTime = new DateTime(2010,11,3);
long shazbot = 1000000000 * DateTime.Day;

shazbot comes out to -1294967296

Huh???

Answer 1

shazbot may be a long, but neither 1000000000 or DateTime.Day are. So, C# does int multiplication first (which results in an overflow) then casts it to a long to store in shazbot.

If you want a long result, make one of them a long, like this:

long shazbot = 1000000000L * DateTime.Day;

Edit: C# gives you a warning if you use l instead of L. Fixed.

Answer 2

Cast to long like this:

long shazbot = 1000000000L * DateTime.Day;