重载运算符写法

class a
{
     public int Num{get;set;}
     //重载运算符 +
     public static a oprator +(a a1,a a2)
    {
          a2.Num+=a1.Num;
          return a2;
    }      
}

a a1=new a(){Num=10};
a a2=new a(){Num=20};
a a3=a1+a2;
console.writeLine(a3.Num);
输出结果为：30