c# 入门语法

一、关于元组

(string name, int age) customer = GetCustomer(); var name = customer.name;

 

var age = 123;

var name = "aa";

var tuple = (age, name); //元组直接用一样的名字

var anon = new { age, name };

 

tuple.age = 12;

tuple.name = "bb";

 

// 用元组可以不用写对象

var t1 = (a: 1, b: 2);

 

二、关于属性

private int Age { get; }

 

// 没必要写

private int age; public int Age { get { return age; } }

 

三、模板字符串

var str = $"prefix {someValue} suffix";

 

四、switch要写default

简化 switch

switch (x) { case 1: return 1 * 1; case 2: return 2 * 2; default: return 0; }

 

return x switch { 1 => 1 * 1, 2 => 2 * 2, _ => 0, };

 

五、哈希码

// 建议用Combine public override int GetHashCode() { return System.HashCode.Combine(base.GetHashCode(), j); }

 

六、用nameof

var n2 = nameof(Int32);

 

七、判空

var v = x ?? y; // x不为空就用x，否则就用y

var v = o?.ToString();

if (value is null) return;

 

八、变量

var obj = new Customer(); // 用var

 

九、方法

public int GetAge()

{

return this.Age;

}

简化方法：

public int GetAge() => this.Age;

 

// 注意方法在编写时候 public static ComplexNumber operator + (ComplexNumber c1, ComplexNumber c2) { return new ComplexNumber(c1.Real + c2.Real, c1.Imaginary + c2.Imaginary); }

 

// 建议去掉花括号和return

public static ComplexNumber operator + (ComplexNumber c1, ComplexNumber c2) => new ComplexNumber(c1.Real + c2.Real, c1.Imaginary + c2.Imaginary);

 

// 索引器属性

public T this[int i] { get { return _values[i]; } }

// 建议修改

public T this[int i] => _values[i];

 

// 避免 as

if (o is int i)

{

// 直接用i 就可以了

// ...

}

var x = i is default(int) or > (default(int)); var y = o is not C c;

 

 

 

int i; if (int.TryParse(value, out i) {...}

 

if (int.TryParse(value, out int i) {...}

 

// 使用默认值

void DoWork(CancellationToken cancellationToken = default) { ... }

// 解构

var (name, age) = GetPersonTuple();

// 使用

string[] names = { "Archimedes", "Pythagoras", "Euclid" };

var index = names[names.Length - 1];

// 有个简化语法 var index = names[^1];

 

string sentence = "the quick brown fox"; var sub = sentence.Substring(0, sentence.Length - 4);

var sub = sentence[0..^4];