Interfaceは参照型

Interfaceは参照型だったよな。と思い確認。

class Program
{
    static void Main(string[] args)
    {

        Struct s = new Struct();
        s.MyProperty = 1;

        Interface i = s;
        i.MyProperty = 2;

        Interface i2 = i;
        i2.MyProperty = 3;

        Console.WriteLine("s :{0}", s.MyProperty);
        Console.WriteLine("i :{0}", i.MyProperty);
        Console.WriteLine("i2:{0}", i2.MyProperty);
    }
}

interface Interface
{
    int MyProperty { get; set; }
}

struct Struct : Interface
{
    public int MyProperty { get; set; }
}

結果

正解。

つまり、Interface型に代入する際にボックス化が行われているということ。

class Program
{
    static void Main(string[] args)
    {
        var val = new Struct();
        var val2 = new Class();

        Stopwatch sw = Stopwatch.StartNew();
        for (int i = 0; i < 1000000000; i++)
        {
            object obj = val;
        }
        Console.WriteLine("struct -> object   :" + sw.Elapsed);
        sw.Reset();
        sw.Start();
        for (int i = 0; i < 1000000000; i++)
        {
            Interface obj = val;
        }
        Console.WriteLine("struct -> Interface:" + sw.Elapsed);
        sw.Reset();
        sw.Start();
        for (int i = 0; i < 1000000000; i++)
        {
            var obj = val;
        }
        Console.WriteLine("struct -> struct   :" + sw.Elapsed);
        sw.Reset();
        sw.Start();
        for (int i = 0; i < 1000000000; i++)
        {
            Interface obj = val2;
        }
        Console.WriteLine("class  -> Interface:" + sw.Elapsed);
        sw.Reset();
        sw.Start();
        for (int i = 0; i < 1000000000; i++)
        {
            object obj = val2;
        }
        Console.WriteLine("class  -> object   :" + sw.Elapsed);
        sw.Reset();
        sw.Start();
        for (int i = 0; i < 1000000000; i++)
        {
            var obj = val2;
        }
        Console.WriteLine("class  -> class    :" + sw.Elapsed);


    }
}

interface Interface
{
    int MyProperty { get; set; }
}

struct Struct : Interface
{
    public int MyProperty { get; set; }
}


class Class : Interface
{
    public int MyProperty { get; set; }
}