Value type and reference type problem
.net, c#, reference-type, swap
Solution
There's various different things here:
- the objects live off in the heap. Forget about them for now
- the references to the objects are what get stored in `First` and second
- you have two variables in `Main`
- you have two parameters in `Swap`
now; the important thing is the difference between "reference type / references", and "pass by reference". They are completely unrelated.
in the line:
Swap(First, Second);
you pass the values of two variables to `Swap`. In this case, the value of `First` / `Second` is the reference to the boxed object.
Next;
private static void Swap(object First, object Second)
{
object temp = First;
First = Second;
Second = temp;
}
Here, you swap the value of two local parameters, but these are completely independent to anything else. If we want the caller to see the change to the values (i.e. reassignment), we need to pass by reference:
private static void Swap(ref object First, ref object Second)
{
object temp = First;
First = Second;
Second = temp;
}
Now the value of `First` is no longer a reference to the boxed object; it is a reference to a reference to the boxed object. At the caller, we use:
Swap(ref First,ref Second);
which means pass the reference of variable `First`, rather than pass the value of variable `First`.
Note that I said you could forget about the fact that there is an object? Everything above is exactly the same if we used:
int x = 1, y = 2;
Swap(ref x, ref y);
void Swap(ref int a, ref int b) {
var tmp = a; a = b; b = tmp;
}
the only difference is that the value of `x` is 1 etc, and `ref x` is a reference to variable x. In pass by reference, reference-type vs value-type is completely irrelevant; the only important thing is understanding that you pass the value of a variable by default, where the value of a variable is `1` (etc), or "a reference to an object". Either way, the logic is the same.
Problem
Hi I'm trying to do a simple swap of two objects.My code is ``` void Main() { object First = 5; object Second = 10; Swap(First, Second); //If I display results it displays as //Value of First as 5 and Second as 10 } private static void Swap(object First, object Second) { object temp = First; First = Second; Second = temp; } ``` Since objects are reference type, its reference should be passed to method and it should swap. why is it not happening?