C# 6.0 新特性汇总

The static using declaration allows invoking static methods without the classname.In C# 5using System;Console.WriteLine("Hello, World!");In C# 6using static System.Console;WriteLine("Hello, World");

With expression-bodied methods, a method that includes just one statement canbe written with the lambda syntax.In C# 5public bool IsSquare(Rectangle rect){return rect.Height == rect.Width;}In C# 6public bool IsSquare(Rectangle rect) => rect.Height == rect.Width;

Similar to expression-bodied methods, one-line properties with only a get accessorcan be written with the lambda syntaxIn C# 5public string FullName{get{return FirstName +"" + LastName;}}In C# 6public string FullName => FirstName +"" + LastName;

In C# 5public class Person{public Person(){Age = 24;}public int Age {get; set;}}In C# 6public class Person{public int Age {get; set;} = 42;}

To implement read-only properties, C# 5 requires the full property syntax. WithC# 6, you can do this using auto-implemented properties.In C# 5private readonly int _bookId;public BookId{get{return _bookId;}}In C# 6public BookId {get;}

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# 5public 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));

The null propagation operator simplifies null checks.In C# 5int? age = p == null ? null : p.Age;var handler = Event;if (handler != null){handler(source, e);}In C# 6int? age = p?.Age;handler?.Invoke(source, e);

The string interpolation removes calls to string.Format. Instead of usingnumbered format placeholders in the string, the placeholders can includeexpressions.In C# 5public override ToString(){return string.Format("{0}, {1}", Title, Publisher);}In C# 6public override ToString() => $"{Title} {Publisher}";

Dictionaries can now be initialized with a dictionary initializer―similar to thecollection initializer.In C# 5var dict = new Dictionary<int, string>();dict.Add(3,"three");dict.Add(7,"seven");In C# 6var dict = new Dictionary<int, string>(){[3] ="three",[7] ="seven"};

In C# 5try{//etc.} catch (MyException ex){if (ex.ErrorCode != 405) throw;// etc.}In C# 6try{//etc.} catch (MyException ex) when (ex.ErrorCode == 405){// etc.}

await can now be used in the catch clause. C# 5 required a workaround.In C# 5bool hasError = false;string errorMessage = null;try{//etc.} catch (MyException ex){hasError = true;errorMessage = ex.Message;} if (hasError){await new MessageDialog().ShowAsync(errorMessage);}In C# 6try{//etc.} catch (MyException ex){await new MessageDialog().ShowAsync(ex.Message);}