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c#boxingunboxing

Are these boxing/unboxing examples

Are 2 and 3 boxing/unboxing examples?

1) The documentation example: 

int i = 123;
object iBoxed = i;
i = (int) iBoxed;

2: Is the boxing/unboxing as well?

int i = 123;
object iBoxed = i;
i = Int32.Parse(iBoxed.ToString());

3: Is the boxing/unboxing as well?

int i = 123;
object iBoxed = i;
i = Convert.ToInt32(iBoxed);

I assume that in all examples technically happens the same.

  1. A value type is created on the stack
  2. A reference is created on the stack, the value is copied to the heap.
  3. The heap value is copied to the reference. The reference gets deleted.

So I guess 2 und 3 are examples for boxing/unboxing?

Solution

  • In all three examples:

    iBoxed is a boxed copy of i.

    In example 2: There is no unboxing involved here, as ToString is a virtual method that will finally resolve to int.ToString, which will then be parsed by int.Parse, returning a non-boxed int on the stack.

    In example 3: iBoxed will get unboxed in the body of the method Convert.ToInt32 and returned as a non-boxed integer, on the stack again.