I'm writing a class with several methods that take integer input. The input values cannot be less than zero. Since we're not on .Net 4.0 yet, I'm manually writing code contracts (that is, my functions check preconditions, e.g. before doing anything else, I write something like…

if (sequenceNumber < 0)
{
    throw new ArgumentOutOfRangeException("sequenceNumber", "Sequence number must be 0 or greater");
}

This got me thinking: why don't we ever use unsigned integers? Seems like having a uint would better communicate the requirement, and would simply not allow a negative number. The main answer seems to be that casting between uint and other data types, which is inevitable, is ugly. And that uint is not CLS compliant. Even though I'm not trying to write CLS-compliant code at the moment, I think I'll stick with int – because that is our existing convention, and I don't see enough reason to change the convention.