原文： http://damieng.com/blog/2013/12/09/probable-c-6-0-features-illustrated
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1. 主构造函数
以更简短的方式写一个构造函数给私有变量赋值.
从前
public class Point {
private int x, y;
public Point(int x, int y)
this.x = x;
this.y = y;
}
}
现在
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. 自动属性赋值
之前
private readonly int x;
public int X { get { return x; } }
现在
public int X { get; } = x; public int XX { get; set; } = xx; 3. using 静态类 引入一个类的所有的公共静态方法;
引入一个类的所有的公共静态方法 .
之前
public double A { get { return Math.Sqrt(Math.Round(5.142)); } }
现在
using System.Math;
...
public double A { get { return Sqrt(Round(5.142)); } }
4. 属性表达式
之前
public double Distance {
get { return Math.Sqrt((X * X) + (Y * Y)); }
}
现在
public double Distance => Math.Sqrt((X * X) + (Y * Y));
思考
- 尽管使用了 => 其实和System.Linq.Expression无关.
5. 方法表达式
之前
public Point Move(int dx, int dy) {
return new Point(X + dx1, Y + dy1);
}
现在
public Point Move(int dx, int dy) => new Point(X + dx, Y + dy);6. Params 参数 支持的类型更多了
之前pararms只支持Array.
之前
Do(someEnum.ToArray());
...
public void Do(params int[] values) { ... }
现在
Do(someEnum);
public void Do(params IEnumerable<Point> points) { ... }7. null 检查
之前
if (points != null) {
var next = points.FirstOrDefault();
if (next != null && next.X != null) return next.X;
}
return -1;
现在
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. 就地声明输出参数
之前
int x;
int.TryParse("123", out x);
现在
int.TryParse("123", out int x);10. 更优雅的string.Format
之前
var s = string.Format("{0} is {1} years{{s}} old", p.Name, p.Age);
现在
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 await
12. 字典的index Initializers
之前
var result = new Dictionary<string, string>()
{{"index1", "value1"},
{"index2", "value2"}};
现在
var result = new Dictionary<string, string>()
{
["index1"] = "value1", ["index2"] = "value2"};