Question

If I assign a simple value type (e.g. an int) to an attribute of type ValueType, is the value then boxed?

For example if I do this:

int i = 4;
ValueType test = i;

Will the value be boxed?

Answer 1

Yes, it will. This is because each type occupies a constant amount of memory at runtime (int takes 4 bytes, for example). A struct will take as much space is required to lay out all of the fields in memory.

Since you can store any value type in ValueType, and since ValueType would have to be exactly the same size as the type you’re assigning to test, the ValueType type is actually a reference type.

Consider:

int a = 0;
long b = 1;

ValueType test;

test = a;
test = b;

This is perfectly valid code. test must occupy a fixed size on the stack, and a and b are different sizes. Hopefully this clarifies why exactly ValueType cannot itself be a value type. (It’s related to the reason why you can’t derive value types.)