C# 填鸭笔记 6

MemberwiseClone , GetType / typeof , Boxing / Unboxing , is , overload operator , IComparable , as

GetType 用在实例上，typeof 用在类上
Console.WriteLine(typeof(Program) == p.GetType());

partial class Program : IA {
...
Program pppp = new Program();
IA aaaa = pppp; // boxing
Program pppp2 = (Program) aaaa; // unboxing

boxing 不需要明确的进行类型转换（子类型到父类型），unboxing需要明确的进行类型转换（父类型到子类型）。

is : 如果一个变量是一个类/接口的子类，孙子类，is 返回 true.
Console.WriteLine('a' is int);
可以通过编译，只是提出一个警告。
重载运算符

        public static Program operator + (Program pp1,Program pp2){
            Program pp = new Program();
            pp.score = pp1.score + pp2.score;
            return pp;
        }
1,必须是静态的，
2,加上关键字： operator
3,不能返回 void
4,true 和 false 必须同时重载。> 和 < 必须同时重载, >= 和 <= 也必须同时重载, == 和 != 必须同时重载.

一元运算的例子：
        public static Program operator +(Program p1){
            Program p = new Program();
            p.score = Math.Abs(p1.score);
            return p;
        }
...
pppp2.score = -40;
Console.WriteLine((+pppp2).score);

可以重载的运算符：

Unary operators: +, -, !, ~, ++, --, true, false
Binary operators: +, -, *, /, %, &, |, ^, <<, >>
Comparison operators: ==, !=, <, >, <=, >=

重载 false / true

        public static bool operator true(Program p1){
            if (p1.score > 1) return true;
            return false;
        }

        public static bool operator false(Program p1){
            if (p1.score > 1) return false;
            else return true;
        }

。。。

            if (pppp2) {
                Console.WriteLine("True {0}",pppp2.score);
            } else {
                Console.WriteLine("False {0}",pppp2.score);
            }

接口：IComparable

partial class Program : IA , IComparable {
。。。。
#region IComparable 成员

        public int CompareTo(object obj) {
            if (obj is Program) {
                return this.score - ((Program)obj).score;
            }else
                throw new NotImplementedException();
        }

#endregion
。。。
Console.WriteLine(Comparer.Default.Compare(pppp2,pppp));
Console.WriteLine("here {0}",pppp.CompareTo(obj));

重载转换操作符

public static implicit operator ConvClass2(ConvClass1 op1)
public static explicit operator ConvClass1(ConvClass2 op1)

    class B : A{
。。。
        public static explicit operator C(B b){ //B 转换成 C ，必须显示的转换。
            C c = new C();
            c.name = b.name;
            return c;
        }
    }

class C {
private string _name;

        public string name {
            set { _name = value;}
            get { return _name; }
        }

        public static implicit operator B(C c){
            B b = new B();
            b.name = c.name;
            return b;
        }

。。。。。。。。。。。。。

B bbb = new B();
C ccc = (C)bbb;//B 转换成 C ，必须显示的转换。

ccc = new C();
bbb = ccc;//可以隐式的转换。

as

This is only possible in certain circumstances:

If <operand> is of type <type>
If <operand> can be implicitly converted to type <type>
If <operand> can be boxed into type <type>
If no conversion from <operand> to <type> is possible, then the result of the expression will be null.

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Last Updated ( Monday, 23 March 2009 18:25 )

重载 false / true

接口：IComparable

重载转换操作符

as

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