设计一个Integer整数类，并使Integer i=8; 语句编译不出错

use implicit, C# codes as below:

using System;

class Integer

{

private Integer(int d) { val = d; }

public int val;

public static implicit operator int(Integer d)

{

return d.val;

}

public static implicit operator Integer(int d)

{

return new Integer(d);

}

}

class Program

{

static void Main(string[] args)

{

Integer dig = 12;

Console.WriteLine(dig);

Console.ReadKey();

}

}