public void MilkCow(AsClassA myAnimal)
{
AsClassD myCow = myAnimal as AsClassD;
if (myCow != null)
{
myCow.Milk();
}
else
{
Console.WriteLine($"{myAnimal.Name} isn't a cow, and so can't be milked.");
}
}
static void Main(string[] args)
{
// 封箱&拆箱
// struct
MyStruct valType1 = new MyStruct();
valType1.Val = 5;
// object 对象副本的引用
object refType = valType1; // 封箱
valType1.Val = 6;
MyStruct valType2 = (MyStruct)refType; // 拆箱
Console.WriteLine($"valType2.Val = {valType2.Val}");
// class
MyClass1 valType3 = new MyClass1();
valType3.Val = 5;
object refType2 = valType3;
valType3.Val = 6;
MyClass1 valType4 = (MyClass1)refType2;
Console.WriteLine($"valType4.Val = {valType4.Val}");
// struct 实现接口将值类型封箱到接口类型
MyStruct valType5 = new MyStruct();
valType5.Val = 5;
IMyInterface refType3 = valType5;
valType5.Val = 6;
MyStruct valType6 = (MyStruct)refType3;
Console.WriteLine($"valType6.Val = {valType6.Val}");
Console.WriteLine();
// is
// <operand> is <type>
Checker check = new Checker();
ClassA try1 = new ClassA();
ClassB try2 = new ClassB();
ClassC try3 = new ClassC();
ClassD try4 = new ClassD();
MyStruct try5 = new MyStruct();
object try6 = try5;
Console.WriteLine("Analyzing ClassA type variable:");
check.Check(try1);
Console.WriteLine("\nAnalyzing ClassB type variable:");
check.Check(try2);
Console.WriteLine("\nAnalyzing ClassC type variable:");
check.Check(try3);
Console.WriteLine("\nAnalyzing ClassD type variable:");
check.Check(try4);
Console.WriteLine("\nAnalyzing MyStruct type variable:");
check.Check(try5);
Console.WriteLine("\nAnalyzing boxed MyStruct type variable:");
check.Check(try6);
Console.WriteLine();
// 值比较
// 运算符重载
AddClass1 op1 = new AddClass1();
op1.val = 5;
AddClass1 op2 = new AddClass1();
op2.val = 5;
bool isSame = op1 == op2; // 是否引用同一个对象, 非验证值相等
AddClass1 op3 = op1 + op2;
AddClass1 op4 = -op1;
Console.WriteLine($"isSame = {isSame}.");
Console.WriteLine($"op1.val + op2.val = {op3.val}.");
Console.WriteLine($"-op1.val = {op4.val}.");
Console.WriteLine();
// 列表排序
ArrayList list = new ArrayList();
list.Add(new Person("Rual", 30));
list.Add(new Person("Donna", 25));
list.Add(new Person("Mary", 27));
list.Add(new Person("Ben", 44));
Console.WriteLine("Unsorted people:");
for (int i = 0; i < list.Count; i++)
{
Console.WriteLine($"{(list[i] as Person).Name} ({(list[i] as Person).Age})");
}
Console.WriteLine();
Console.WriteLine("People sorted with nondefault comparer (by name):");
list.Sort(PersonComparerName.Default);
for (int i = 0; i < list.Count; i++)
{
Console.WriteLine($"{(list[i] as Person).Name} ({(list[i] as Person).Age})");
}
// 转换
ConvClass1 conv1 = new ConvClass1();
conv1.val = 3;
ConvClass2 conv2 = conv1; // implicit 隐式转换
ConvClass2 conv3 = new ConvClass2();
conv3.val = 3;
// conv3.val = 3e15; // System.OverflowException
ConvClass1 conv4 = (ConvClass1)conv3; // explicit 显式转换
// as
Console.WriteLine();
AsClassA MyAnimal = new AsClassA();
AsClassD MyCow = MyAnimal as AsClassD;
// MyAnimal ==null
AsClassD MyCow2 = new AsClassD();
AsClassA MyAnimal2 = MyCow2;
AsClassD MyNewCow2 = MyAnimal2 as AsClassD;
// MyNewCow2 包含 MyCow2引用
MyCow2.MilkCow(MyCow2);
MyCow2.MilkCow(MyNewCow2);
Console.ReadKey();
}