Probable C# 6.0 features illustrated

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原文： http://damieng.com/blog/2013/12/09/probable-c-6-0-features-illustrated

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1. 主建構函式

以更簡短的方式寫一個建構函式給私人變數賦值.

從前

public class Point {    private int x, y;    public Point(int x, int y)        this.x = x;        this.y = y;    }}

現在

public class Point(int x, int y) {    private int x, y;}

Thoughts

• Do you need to independently define x and y?
• Can you still write a body?
• How would you make the default private?

This solution feels too constrained, would have preferred something like:

public Point(set int x, set int y)

That set the property and optionally created a private one if it didn’t. Would allow bodies, use on multiple constructors etc.

2. 自動屬性賦值之前

private readonly int x;public int X { get { return x; } }

現在

public int X { get; } = x;  

public int XX { get; set; } = xx; 

3. using 靜態類 引入一個類的所有的公用靜態方法;

引入一個類的所有的公用靜態方法 .

之前

public double A { get { return Math.Sqrt(Math.Round(5.142)); } }

現在

using System.Math;...public double A { get { return Sqrt(Round(5.142)); } }

 4. 屬性運算式之前

public double Distance {    get { return Math.Sqrt((X * X) + (Y * Y)); }}

現在

public double Distance => Math.Sqrt((X * X) + (Y * Y));

思考

• 儘管使用了 => 其實和System.Linq.Expression無關.

5. 方法運算式之前

public Point Move(int dx, int dy) {    return new Point(X + dx1, Y + dy1);}

現在

public Point Move(int dx, int dy) => new Point(X + dx, Y + dy);

6. Params 參數 支援的類型更多了

之前pararms只支援Array.

之前

Do(someEnum.ToArray());...public void Do(params int[] values) { ... }

現在

Do(someEnum);public void Do(params IEnumerable<Point> points) { ... }

7. null 檢查之前

if (points != null) {    var next = points.FirstOrDefault();    if (next != null && next.X != null) return next.X;}   return -1;

現在

var bestValue = points?.FirstOrDefault()?.X ?? -1;
int? first = customers?[0].Orders?.Count()

8. Constructor type parameter inference

Removes the need to create static factory methods to infer generic types. This is helpful with Tuples etc.

Before

var x = MyClass.Create(1, "X");...public MyClass<T1, T2> Create<T1, T2>(T1 a, T2 b) {    return new MyClass<T1, T2>(a, b);}

After

var x = new MyClass(1, "X");

Thoughts

• Another great addition.
• Does it understand list and collection initializers to automatically determine the generic types too?

9. 就地聲明輸出參數之前

int x;int.TryParse("123", out x);

現在

int.TryParse("123", out int x);

10. 更優雅的string.Format之前

var s = string.Format("{0} is {1} years{{s}} old", p.Name, p.Age);

現在

var s = "\{p.Name} is \{p.Age} year{s} old";

var s = "\{p.Name, 20} is \{p.Age:D3} year{s} old";

var s = "\{p.Name} is \{p.Age} year\{(p.Age == 1 ? "" : "s")} old";

var s = $"{p.Name} is {p.Age:D3} year{{s}} old";

11. 可以在catch finally 中使用 await12. 字典的index Initializers之前

var result = new Dictionary<string, string>()
{

　　{"index1", "value1"},

　　{"index2", "value2"}
};

現在

var result = new Dictionary<string, string>()
{

　　["index1"] = "value1",

　　["index2"] = "value2"

};

Probable C# 6.0 features illustrated