How come changes to properties of value types persisted across method calls only if..
I know that when it comes to references types (ie: classes), changes to properties of said reference types are persisted across method calls, regardless of the type of the property.
I recently noticed that the same is not true for value types (ie: structs). That is, changes to properties of value types are persisted across method calls only if said properties are non-built in reference types.
For example:
Code:
namespace N
{
class M
{
public int k = 0;
}
class C
{
public string s;
public int i;
public M m;
public C(string s, int i, M m)
{
this.s = s;
this.i = i;
this.m = m;
}
}
struct S
{
public string s;
public int i;
public M m;
public S(string s, int i, M m)
{
this.s = s;
this.i = i;
this.m = m;
}
}
class Program
{
static void Main()
{
C c = new C("A", 0, new M());
S s = new S("A", 0, new M());
Console.WriteLine(c.s + ", " + c.i + ", " + c.m.k); //A, 0, 0
Console.WriteLine(s.s + ", " + s.i + ", " + s.m.k); //A, 0, 0
Change(c);
Change(s);
Console.WriteLine(c.s + ", " + c.i + ", " + c.m.k); //AA, 1, 1
Console.WriteLine(s.s + ", " + s.i + ", " + s.m.k); //A, 0, 1
Console.ReadKey();
}
static void Change(C x)
{
x.s = "AA";
x.i++;
x.m.k++;
}
static void Change(S x)
{
x.s = "AA";
x.i++;
x.m.k++;
}
}
}
Not sure if the above code will compile (maybe I made typos somewhere :)). But if it does compile you will find that changes to properties of value types persisted across method calls only in cases where those properties are non-built-in reference types. How come?
