Question

I am wondering if the following expressions are equivalent (In C#):

float x = ... ;
int y = ... ;

var result = (float) (x / y);

Versus:

var result = x / (float)y;

Where can i read more about this specific topic?

What i am interested in is:

1. Will these always produce the same result?
2. Does one option perform more efficiently than the other?

Answer 1

Yes, they will behave the same way. In fact, you can just use:

var result = x / y;

or

float result = x / y;

Section 7.8.2 of the C# 4 spec shows which division operators are avaiable – and there’s no float operator /(float, int) operator. Instead, the C# compiler uses the implicit conversion from int to float, and uses the float operator /(float, float) operator.

This is just normal operator overload resolution (spec section 7.3.4) and implicit numeric conversions (spec section 6.1.2).

When in doubt consult the spec. I have a web page with links to the different versions; the C# 5 spec is bundled with VS 2012 but there’s no separate download for it right now.