转换（重载转换运算符）

 1  class A
 2     {
 3         public int intNumber;
 4         public static implicit operator B(A a)
 5         {
 6             B b = new B();
 7             b.doubleNumber = a.intNumber;
 8             return b;
 9         }
10     }
11     class B
12     {
13         public double doubleNumber;
14         public static explicit operator A(B b)
15         {
16             A a = new A();
17             checked { a.intNumber = (int)b.doubleNumber; }
18             return a;
19         }
20     }
21     class Program
22     {
23         static void Main(string[] args)
24         {
25             A a = new A();
26             a.intNumber = 4;
27             B b = a;
28             Console.WriteLine(b.doubleNumber.ToString());
29         }
30     }