string ddd = ""; //先申明变量
ccc.StringOut(out ddd);
Console.WriteLine(ddd);

StringOut(out string ddd); //传递的同时申明
Console.WriteLine(ddd);
Console.ReadLine();

static void Main(string[] args)
 {
 var data = GetFullName();
 Console.WriteLine(data.Item1);
 Console.WriteLine(data.Item2);
 Console.WriteLine(data.Item3);
 Console.ReadLine();
}
static Tuple<string, string, string> GetFullName() 
{
 return new Tuple<string, string, string>("a", "b", "c");
}

 static void Main(string[] args)
 {
 var data=GetFullName();
 Console.WriteLine(data.a); //可用命名获取到值
 Console.WriteLine(data.b);
 Console.WriteLine(data.c);
 Console.ReadLine();

 }


 //方法定义为多个返回值,并命名
 private static (string a,string b,string c) GetFullName()
 {
 return ("a","b","c");
 }

 static void Main(string[] args)
 {
 //定义解构元组
 (string a, string b, string c) = GetFullName();

 Console.WriteLine(a);
 Console.WriteLine(b);
 Console.WriteLine(c);
 Console.ReadLine();

 }


 private static (string a,string b,string c) GetFullName()
 {
 return ("a","b","c");
 }

object a = 1;
if (a is int) //is判断
{
 int b = (int)a; //拆
 int d = b+10; //加10
 Console.WriteLine(d); //输出
}

object a = 1;
if (a is int c) //这里,判断为int后就直接赋值给c
{
 int d = c + 10;
 Console.WriteLine(d);
}

 static dynamic Add(object a)
 {
 dynamic data;
 switch (a)
 {
 case int b:
  data=b++;
  break;
 case string c:
  data= c + "aaa";
  break;
 default:
  data = null;
  break;
 }
 return data;
 }

object a = 1;
var data= Add(a);
Console.WriteLine(data.GetType());
Console.WriteLine(data);

object a = "bbbb";
var data= Add(a);
Console.WriteLine(data.GetType());
Console.WriteLine(data);

 switch (a)
 {
 case int b when b < 0:
  data = b + 100;
  break;
 case int b:
  data=b++;
  break;
 case string c:
  data= c + "aaa";
  break;
 default:
  data = null;
  break;
 }

 public static void DoSomeing()
 {
 //调用Dosmeing2
 int data = Dosmeing2(100, 200);
 Console.WriteLine(data);
 //定义局部函数,Dosmeing2.
 int Dosmeing2(int a, int b)
 {
 return a + b;
 }
 }

 public void CreateCaCheContext() => new CaCheContext();
 //等价于下面的代码
 public void CreateCaCheContext()
 {
 new CaCheContext();
 } 

// 构造函数的表达式写法
public CaCheContext(string label) => this.Label = label;

// 析构函数的表达式写法
~CaCheContext() => Console.Error.WriteLine("Finalized!");

private string label;

// Get/Set属性访问器的表达式写法
public string Label
{
 get => label;
 set => this.label = value ?? "Default label";
}

 public string IsNull()
 {
 string a = null;
 if (a == null)
 {
 throw new Exception("异常了!");
 }
 return a;
 }

 public string IsNull()
 {
 string a = null;
 return a ?? throw new Exception("异常了!");
 }

 public class CaCheContext
 {
 public ValueTask<int> CachedFunc()
 {
 return (cache) ? new ValueTask<int>(cacheResult) : new ValueTask<int>(loadCache());
 }
 private bool cache = false;
 private int cacheResult;
 private async Task<int> loadCache()
 {
 // simulate async work:
 await Task.Delay(5000);
 cache = true;
 cacheResult = 100;
 return cacheResult;
 }
 }

 //main方法可不能用async修饰,所以用了委托.
 static void Main(string[] args)
 {
 Action act = async () =>
 {
 CaCheContext cc = new CaCheContext();
 int data = await cc.CachedFunc();
 Console.WriteLine(data);
 int data2 = await cc.CachedFunc();
 Console.WriteLine(data2);
 };
 // 调用委托 
 act();
 Console.Read();

 }

 int a = 123_456;
 int b = 0xAB_CD_EF;
 int c = 123456;
 int d = 0xABCDEF;
 Console.WriteLine(a==c);
 Console.WriteLine(b==d);
 //如上代码会显示两个true,在数字中用"_"分隔符不会影响结果,只是为了提高可读性