I am a bit confused with a concept of value types as properties in a class. As far as I understand, when getter is called - a copy of value type is returned. Let's have an example:
public struct Point
{
public int X;
public int Y;
public void Set(int x, int y)
{
X = x;
Y = y;
}
}
public class Test
{
public Int32 X { get; set; }
public void SetX(int x) => X = x;
public Point Point { get; set; }
}
static void Main(string[] args)
{
var test = new Test();
test.SetX(10);
test.Point.Set(20, 30);
Console.WriteLine(test.X);
Console.WriteLine($"{test.Point.X} {test.Point.Y}");
}
Point is not modified, since it is a value type, and getter gives us a copy, which makes sense. The thing I don't understand - why in this case X is modified? It is a value type also. This looks like a contradiction to me. Please help me to understand what I am missing
Point is not modified, since it is a value type, and getter gives us a copy, which makes sense
Yes, because you get a make changes to local copy of Point returned by auto-property getter.
The thing I don't understand - why in this case X is modified?
Because you are modifying object containing X not the copy of X. X = x invokes setter (there is no "returns copy" happening here) for auto-property which will write corresponding value to corresponding memory location.
Code for Point simulating this behavior can look for example like:
public void SetPoint(int x, int y) => Point = new Point{X= x, Y =y};
And in both cases the following will work:
test.X = 42;
test.Point = new Point {X = 7, Y = 42}