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];