C#语法糖个人笔记

1. 经过简化的Property

普通：

private string _myName;
public string MyName
{
    get { return _myName; }
    set { _myName = value; }
}

语法糖：

public string MyName { get; set; }
public string MyName { get; set; } = "张三";
public string MyName { protected get; private set; }

2. 取list中的值

普通：

foreach (string str in listString)
{
	Console.WriteLine(str);
}

语法糖：

listString.ForEach(s => Console.WriteLine(s));

3. 字符串嵌入值

普通：

var str=string.Format("时间：{0}", DateTime.Now);

语法糖：

var str=$"时间：{DateTime.Now}";

4. 问号(?)表达式

4.1 可空类型修饰符（？）

普通：

Nullable<int> intOne = 5;

语法糖：

int? intTwo = 5;

4.2 合并运算符(??)

语法糖：当前面为空是将后面的值进行赋值

int intA = null;
int intB = intA ?? 0;

4.3 NULL检查运算符（?.）

语法糖：当对象为空，直接返回，不为空返回值

string str = "abcd";
Console.WriteLine(str?.Length);// 输出 4

4.4 "?[]"运算符

5. 自动释放资源(using)

普通：

// try finally 写法
SqlConnection conn = null;
try
{
	conn = new SqlConnection("数据库连接字符串");
	conn.Open();
}
finally
{
	conn.Close();
	conn.Dispose();
}

语法糖：

using (SqlConnection conn=new SqlConnection("数据库连接字符串"))
{
      conn.Open();
}

6. 成员索引

语法糖：

    public class Product
    {
        public string this[string color]
        {
            get { return String.Format("{0}经典长袖衬衫", color); }
        }
    }
    public static main()
    {
    	Product product = new Product();
    	string str = product["白色"];//这里输出 白色经典长袖衬衫
    }

7. 在属性/方法中使用lambda

语法糖：

1 public string NameFormat => string.Format("姓名: {0}", "summit");
2 public void Print() => Console.WriteLine(Name);

8. 静态类的导入

语法糖：

using static System.Console;
class Program 
{ 
　　static void Main(string[] args) 
　　{
　　　　WriteLine("hello wolrd"); 
　　}
}

9.元组和弃元

元组语法糖：

var xs = new[] { 4, 7, 9 };
var limits = FindMinMax(xs);
Console.WriteLine($"Limits of [{string.Join(" ", xs)}] are {limits.min} and {limits.max}");
// Output:
// Limits of [4 7 9] are 4 and 9

var ys = new[] { -9, 0, 67, 100 };
var (minimum, maximum) = FindMinMax(ys);
Console.WriteLine($"Limits of [{string.Join(" ", ys)}] are {minimum} and {maximum}");
// Output:
// Limits of [-9 0 67 100] are -9 and 100

(int min, int max) FindMinMax(int[] input)
{
    if (input is null || input.Length == 0)
    {
        throw new ArgumentException("Cannot find minimum and maximum of a null or empty array.");
    }

    var min = int.MaxValue;
    var max = int.MinValue;
    foreach (var i in input)
    {
        if (i < min)
        {
            min = i;
        }
        if (i > max)
        {
            max = i;
        }
    }
    return (min, max);
}

10.switch表达式

语法糖：

public static RGBColor FromRainbow(Rainbow colorBand) =>
    colorBand switch
    {
        Rainbow.Red    => new RGBColor(0xFF, 0x00, 0x00),
        Rainbow.Orange => new RGBColor(0xFF, 0x7F, 0x00),
        Rainbow.Yellow => new RGBColor(0xFF, 0xFF, 0x00),
        Rainbow.Green  => new RGBColor(0x00, 0xFF, 0x00),
        Rainbow.Blue   => new RGBColor(0x00, 0x00, 0xFF),
        Rainbow.Indigo => new RGBColor(0x4B, 0x00, 0x82),
        Rainbow.Violet => new RGBColor(0x94, 0x00, 0xD3),
        _              => throw new ArgumentException(message: "invalid enum value", paramName: nameof(colorBand)),
    };

元组模式：

public static string RockPaperScissors(string first, string second)
    => (first, second) switch
    {
        ("rock", "paper") => "rock is covered by paper. Paper wins.",
        ("rock", "scissors") => "rock breaks scissors. Rock wins.",
        ("paper", "rock") => "paper covers rock. Paper wins.",
        ("paper", "scissors") => "paper is cut by scissors. Scissors wins.",
        ("scissors", "rock") => "scissors is broken by rock. Rock wins.",
        ("scissors", "paper") => "scissors cuts paper. Scissors wins.",
        (_, _) => "tie"
    };

11.匹配模式

语法糖：

public static bool IsLetter(this char c) =>
    c is >= 'a' and <= 'z' or >= 'A' and <= 'Z';