C# Integer casting

Question

I'm trying to do the following

int num = 20;
object number = num;
int result = (int)num;

It's yelling "Invalid cast" at me because, from what the compiler says:

Unable to cast object of type 'System.Int64' to type 'System.Int32

Can you please explain why my Int32 became an Int64?

https://stackoverflow.com/questions/39891504/casting-object-to-int-throws-invalidcastexception-in-c-sharp — David Tansey, Aug 02 '19 at 15:11
[dotnetfiddle](https://dotnetfiddle.net/KfR1mc) ← Code works fine. — Igor, Aug 02 '19 at 15:11
I suspect that the code you post is slightly different than the real problem. Are you perhaps trying to cast a `long` to an `object` and then to an `int`? — D Stanley, Aug 02 '19 at 15:13
@itsme86: why you are suprised? The variable `number` is never used and `num` is still `20`. @OP: Show the real code — Tim Schmelter, Aug 02 '19 at 15:14

score 1 · Answer 1 · answered Aug 02 '19 at 15:12

object number = num; is not a cast, but boxing!

While all reference types inherit from Object - explicitly or implicitly Value Types do not have a inheritance chain. Instead they get boxed into a instance of...something. That is then cast into the object.

And apparently that instance takes Int64 rather then Int32. For one reason or another, the option to put a Int32 into a Box that takes only Int32 is never even considered.

There is no longer a real reason to do this anyway. With things like Generics, you can get around most needs to box value types ever.

C# Integer casting

1 Answers1