一.out的形參變數無需再提前聲明 befor: after: 二.擴展了元組(Tuple的使用,需要Nuget引用 System.ValueTuple) 1.命名的改進: ①.無命名,僅能通過無意義的Item1,Item2進行訪問: befor: after: 混合型命名:(會有一個編譯警告,僅以 ...
一.out的形參變數無需再提前聲明
befor:
string input = "3"; int numericResult; if (int.TryParse(input, out numericResult)) Console.WriteLine(numericResult); else Console.WriteLine("Could not parse input");
after:
string input = "3"; if (int.TryParse(input, out var numericResult)) Console.WriteLine(numericResult); else Console.WriteLine("Could not parse input");
二.擴展了元組(Tuple的使用,需要Nuget引用 System.ValueTuple)
1.命名的改進:
①.無命名,僅能通過無意義的Item1,Item2進行訪問:
var letters = ("a", "b"); Console.WriteLine($"Value is {letters.Item1} and {letters.Item2>}");
befor:
(string first, string second) letters = ("a", "b"); Console.WriteLine($"Value is {letters.first} and {letters.second}");
after:
var letters = (first: "a",second: "b"); Console.WriteLine($"Value is {letters.first} and {letters.second}");
混合型命名:(會有一個編譯警告,僅以左側命名為準)
(string leftFirst,string leftSecond) letters = (first: "a", second: "b"); Console.WriteLine($"Value is {letters.leftFirst} and {letters.leftSecond}");
2.函數返回元組、對象轉元組
static void Main(string[] args) { var p = GetData(); Console.WriteLine($"value is {p.name} and {p.age}"); } private static (string name,int age) GetData() { return ("han mei", 23); }
三.Local function (本地函數)
static void Main(string[] args) { var v = Fibonacci(3); Console.WriteLine($"value is {v}"); } private static int Fibonacci(int x) { if (x < 0) throw new ArgumentException("Less negativity please!", nameof(x)); return Fib(x).current; (int current, int previous) Fib(int i) { if (i == 0) return (1, 0); var (p, pp) = Fib(i - 1); return (p + pp, p); } }
四.Literal improments(字義改進)
1.數字間可以增加分隔符:_ (增加可讀性)
2.可以直接聲明二進位 (使用二進位的場景更方便,比如掩碼、用位進行許可權設置等)
var d = 123_456; var x = 0xAB_CD_EF; var b = 0b1010_1011_1100_1101_1110_1111;
五.Ref returns and locals (返回引用[返回的變數可以是一個引用])
static void Main(string[] args) { int[] array = { 1, 15, -39, 0, 7, 14, -12 }; ref int place = ref Find(7, array); // aliases 7's place in the array place = 9; // replaces 7 with 9 in the array Console.WriteLine(array[4]); // prints 9 } private static ref int Find(int number, int[] numbers) { for (int i = 0; i < numbers.Length; i++) { if (numbers[i] == number) { return ref numbers[i]; // return the storage location, not the value } } throw new IndexOutOfRangeException($"{nameof(number)} not found"); }
六.More expression bodied members(更多的表達式體的成員)
支持更多的成員使用表達式體,加入了訪問器、構造函數、析構函數使用表達式體
class Person { private static ConcurrentDictionary<int, string> names = new ConcurrentDictionary<int, string>(); private int id = 123; public Person(string name) => names.TryAdd(id, name); // constructors ~Person() => names.TryRemove(id, out var v); // destructors public string Name { get => names[id]; // getters set => names[id] = value; // setters } }
七.Throw expressions(拋出表達式)
將異常直接作為表達式拋出,不管是用表達式體時,還是普通的return 時可以直接作為一個表達式來寫。
class Person { public string Name { get; } public Person(string name) => Name = name ?? throw new ArgumentNullException(name); public string GetFirstName() { var parts = Name.Split(' '); return (parts.Length > 0) ? parts[0] : throw new InvalidOperationException("No name!"); } public string GetLastName() => throw new NotImplementedException(); }
八.Generalized async return types(全面非同步返回類型)
需要Nuget引用System.Threading.Tasks.Extensions。非同步時能返回更多的類型。
public async ValueTask<int> Func() { await Task.Delay(100); return 5; }
九.Pattern matching(模式匹配)
1. is 表達式 ,判斷類型的同時創建變數
public static int DiceSum2(IEnumerable<object> values) { var sum = 0; foreach(var item in values) { if (item is int val) sum += val; else if (item is IEnumerable<object> subList) sum += DiceSum2(subList); } return sum; }
2. switch 表達式,允許case後的條件判斷的同時創建變數
public static int DiceSum5(IEnumerable<object> values) { var sum = 0; foreach (var item in values) { switch (item) { case 0: break; case int val: sum += val; break; case PercentileDie die: sum += die.Multiplier * die.Value; break; case IEnumerable<object> subList when subList.Any(): sum += DiceSum5(subList); break; case IEnumerable<object> subList: break; case null: break; default: throw new InvalidOperationException("unknown item type"); } } return sum; }
參考內容:https://www.cnblogs.com/dev2007/p/6526261.html