Question

Handling integer overflow is a common task, but what’s the best way to handle it in C#? Is there some syntactic sugar to make it simpler than with other languages? Or is this really the best way?

int x = foo();
int test = x * common;
if(test / common != x)
    Console.WriteLine("oh noes!");
else
    Console.WriteLine("safe!");

Answer 1

I haven’t needed to use this often, but you can use the checked keyword:

int x = foo();
int test = checked(x * common);

Will result in a runtime exception if overflows. From MSDN:

In a checked context, if an expression produces a value that is
outside the range of the destination type, the result depends on
whether the expression is constant or non-constant. Constant
expressions cause compile time errors, while non-constant expressions
are evaluated at run time and raise exceptions.

I should also point out that there is another C# keyword, unchecked, which of course does the opposite of checked and ignores overflows. You might wonder when you’d ever use unchecked since it appears to be the default behavior. Well, there is a C# compiler option that defines how expressions outside of checked and unchecked are handled: /checked. You can set it under the advanced build settings of your project.

If you have a lot of expressions that need to be checked, the simplest thing to do would actually be to set the /checked build option. Then any expression that overflows, unless wrapped in unchecked, would result in a runtime exception.