Why can I not modify the result of an unboxing conversion?

Question

struct Point
{
    public int x;
    public int y;
}
void Main()
{
    Point p;
    p.x = 1;
    p.y = 1;
    Object o = p;
    ((Point) o).x = 4; // error
    ((Poi         


        

Answer 1

You can accomplish this using the System.Runtime.CompilerService.Unsafe.Unbox function:

    static void Main()
    {
        Point p;
        p.x = 1;
        p.y = 1;
        Object o = p;
        Unsafe.Unbox(o).x = 6; // error
        p = (Point)o;  // 6
        Console.WriteLine(p.x);
    }

As the documentation notes, and I presume the reason it is considered unsafe, is that you must not do this with an immutable built-in type [e.g. Unbox(i) = 42], and the system does nothing to enforce this.