C# 6.0 11个新特性

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  1. 静态using(static using)


The static using declaration allows invoking static methods without the classname.

In C# 5

using System;Console.WriteLine("Hello, World!");

In C# 6

using static System.Console;WriteLine("Hello, World");

2. 表达式方法(Expression-Bodied Methods)


With expression-bodied methods, a method that includes just one statement canbe written with the lambda syntax.

In C# 5

public bool IsSquare(Rectangle rect){ return rect.Height == rect.Width;}

In C# 6

public bool IsSquare(Rectangle rect) => rect.Height == rect.Width;

3. 表达式属性(Expression-Bodied Properties)


Similar to expression-bodied methods, one-line properties with only a get accessorcan be written with the lambda syntax

In C# 5

public string FullName{ get { return FirstName +"" + LastName; }}

In C# 6

public string FullName => FirstName +"" + LastName;

4. 自动属性初始化器(Auto-Implemented Property Intializers)


Auto-implemented properties can be initialized with a property initializer.

In C# 5

public class Person{ public Person() { Age = 24; } public int Age {get; set;}}

In C# 6

public class Person{ public int Age {get; set;} = 42;}

5. 只读自动属性(Read-Only Auto Properties)

C# 5需要完整的属性语法实现只读属性,C# 6可以使用自动属性实现。

To implement read-only properties, C# 5 requires the full property syntax. WithC# 6, you can do this using auto-implemented properties.

In C# 5

private readonly int _bookId;public BookId{ get { return _bookId; }}

In C# 6

public BookId {get;}

6. nameof操作符(nameof Operator)


With the new nameof operator, names of fields, properties, methods, or types canbe accessed. With this, name changes are not missed with refactoring.

In C# 5

public void Method(object o){ if (o == null) throw new ArgumentNullException("o");In C# 6public void Method(object o){ if (o == null) throw new ArgumentNullException(nameof(o));

7. Null传递操作符(Null Propagation Operator)


The null propagation operator simplifies null checks.

In C# 5

int? age = p == null ? null : p.Age;var handler = Event;if (handler != null){ handler(source, e);}

In C# 6

int? age = p?.Age;handler?.Invoke(source, e);

8. 字符串插值(String Interpolation)


The string interpolation removes calls to string.Format. Instead of usingnumbered format placeholders in the string, the placeholders can includeexpressions.

In C# 5

public override ToString(){ return string.Format("{0}, {1}", Title, Publisher);}

In C# 6

public override ToString() => $"{Title} {Publisher}";

9. 字典初始化器(Dictionary Initializers)


Dictionaries can now be initialized with a dictionary initializer—similar to thecollection initializer.

In C# 5

var dict = new Dictionary<int, string>();dict.Add(3,"three");dict.Add(7,"seven");

In C# 6

var dict = new Dictionary<int, string>(){ [3] ="three", [7] ="seven"};

10. 异常过滤器(Exception Filters)


Exception filters allow you to filter exceptions before catching them.

In C# 5

try{ //etc.} catch (MyException ex){ if (ex.ErrorCode != 405) throw; // etc.}In C# 6try{ //etc.} catch (MyException ex) when (ex.ErrorCode == 405){ // etc.}

11. 在Catch使用Await(Await in Catch)

await可以在catch块中直接使用,C# 5中需要变通使用。

await can now be used in the catch clause. C# 5 required a workaround.

In C# 5

bool hasError = false;string errorMessage = null;try{ //etc.} catch (MyException ex){ hasError = true; errorMessage = ex.Message;} if (hasError){ await new MessageDialog().ShowAsync(errorMessage);}

In C# 6

try{ //etc.} catch (MyException ex){ await new MessageDialog().ShowAsync(ex.Message);}