C# 6.0 新特性汇总

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

 With expression-bodied methods, a method that includes just one statement can be 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;

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

 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; }

 To implement read-only properties, C# 5 requires the full property syntax. With C# 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;}

 With the new nameof operator, names of fields, properties, methods, or types can be 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# 6 public void Method(object o) { if (o == null) throw new ArgumentNullException(nameof(o));

 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);

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

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

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