c#6.0 new Features

I. Development history of C #

It is helpful to understand C # 's understanding of the evolution of C # over the years, by collating and listing the time and the new features of each important update in C #.

Ii. New characteristics of c#6.0

1, string interpolation (string interpolation)

String stitching Optimization

Before:

var Name = "Joye.net"; var Results = "Hello" + name;//direct concatenation var results1 = string. Format ("Hello {0}", Name);//format stitching

After:

var results2 = $ "Hello {Name}"; $ splicing var results= $ "Hello {name}{new program (). Getcnblogssite ()} ";//{} can be inserted directly into the code

2, NULL check operator "?. "(monadic null checking)

Null optimizations

Before:

        public static string Getcnblogssite ()        {            return ' HTTP://WWW.CNBLOGS.COM/YINRQ ';        

Program Pro = Null;if (pro!=null)      Console.WriteLine (Getcnblogssite ());

After:

program pro = NULL; Console.WriteLine (pro?. Getcnblogssite ());

3. Automatic property initializer (initializers for auto-properties)

You can assign values to automatic attributes directly, and do not need to be written in the constructor.

Before:

    public class ClassA    {        private string name{get;set;};        Public ClassA ()        {            Name = "joye.net";        }     }

After:

    public class ClassA    {public        string Name {get; set;} = "Joye.net";       }

4. Read-only automatic attributes (Getter-only auto-properties)

Read-only automatic attributes can be initialized directly or initialized in constructors.

Before

Reduce access to automatic properties public    class ClassA    {public        string Name {get; private set;}       }    c#1.0 implement public    class ClassA    {        private string Name = "Joye.net";        public string name        {            get {return Name;}        }    }

After

    public class ClassA    {public        string Name {get;} = "Joye.net";    }

5, Expression method Body (property Expressions && method Expressions)

Read-only properties, read-only indexers, and methods can all use lambda expressions as body.

The method body of a sentence can be written directly into the arrow function, but no longer need curly braces (the paging control http://www.cnblogs.com/yinrq/p/5586841.html is used to attribute Expression property Expressions)

    public class Pagerinbase {//<summary>///        Current page//</summary> public        int PageIndex { Get Set }//<summary>///page///        </summary> public        int PageSize {get; set;}
         The previous wording
public int Skip{get{return (PageIndex-1) * PageSize}}
               Skips a specified number of elements in a sequence public        int skip = (PageIndex-1) * PageSize;        <summary>//Request URL///        </summary> public        String requeturl = System.Web.HttpContext.Current.Request.Url.OriginalString;        <summary>/        //The constructor initializes the current page and number of pages///        </summary> public        pagerinbase ()        {            if ( PageIndex = = 0) PageIndex = 1;            if (PageSize = = 0) PageSize = ten;        }    }

Method expression (Methods Expressions)

        Before full method public        int Skip ()        {             return (PageIndex-1) * PageSize        }        //after c#6.0 method Expression        public int Skip () = (PageIndex-1) * PageSize;

6. Using static class (static type using statements)

Using System; using static System.Math; Namespace ConsoleApplication1    {        class program        {            static void Main (string[] args)            {                Console.WriteLine (LOG10 (5) + PI);}}}    

7. Check method parameter nameof expression (nameof expressions)

This is useful when you write a property change notification for a viewmodel layer in WPF, you need to write a string, or use a Help method in a library such as Mvvmlight, you can pass in the property directly, but because it is parsed at run time, there is a slight performance penalty. The nameof operator is now used to ensure refactoring security and readability, while improving performance.

Before:

        public static void Add (person person)        {            if (person = = null)            {                throw new ArgumentNullException ("person") ;            }        }

After:

        public static void Add (person person)        {            if (person = = null)            {                throw new ArgumentNullException ( Nameof ("person"));            }        }

8, indexed object initializer (index initializers)

Initializing an object directly from an index

var dic = new Dictionary<int, string> {[0]= "joye.net", [1]= "http://yinrq.cnblogs.com/", [2]= "Index Initializers"} ;

9. Use await in catch and finally (await in catch and finally)

In c#5.0, the await keyword cannot appear in catch and finnaly blocks. and c#6.0 can

            Try            {                res = await resource.openasync (...);//You could does this            }            catch (Resourceexception e)            {                Await Resource.logasync (res, E); Now, can do this            }            finally            {                if (res! = NULL)                    await Res. Closeasync (); Finally and do the.             }

10, inline out parameters (inline declarations for out params)

Before

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

After

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

11. struct constructor without parameters (parameterless constructors in structs)

    public struct MyStruct    {public        int A {get;}        public int B {get;}        Public mystruct (int a, int b) {a = A; b = b; } public        MyStruct (): This (0, 1) {}    }

     WriteLine (New MyStruct (). ToString ());     WriteLine (Default (MyStruct). ToString ());

Third, the Code

Using system;using system.collections.generic;using static system.console;namespace consoleapplication1{public class        MyClass {public int A {get; set;}        public int B {get; set;} = 1;        public string Separator {get;} = "/"; public string Separatorspaces {get;} = String.        Empty;        public double Value = = (double) A/b; public int This[int Index] = index = = 0?        A:B; public int this[string index] = = Index = = "A"?        A:B;        public override string ToString () = "{a}{separatorspaces}{separator}{separatorspaces}{b}";        public void Print () = WriteLine (ToString ());            Public MyClass () {} public MyClass (int a, int b) {a = A;        b = b; } public MyClass (int A, int. B, String separatorspaces): This (A, b) {separatorspaces = separator            Spaces; if (string. IsNullOrEmpty (separatorspaces)) {throw new ARgumentnullexception (nameof (separatorspaces)); }} public static readonly dictionary<string, myclass> Dic = new dictionary<string, MYCL ass> {["zero"] = new MyClass (), ["one"] = new MyClass (1, 1), [ "Half"] = new MyClass (1, 2), ["quarter"] = new MyClass (1, 4), ["infinity"] = new MyClass (1,    0),};        } public struct MyStruct {public int A {get;}        public int B {get;} Public mystruct (int a, int b) {a = A; b = b;    Public MyStruct (): This (0, 1) {} public override string ToString () = "{a}{b}";            } class Program {static void Main (string[] args) {foreach (var f in myclass.dic)            {WriteLine ("{F.key}: {f.value.value}");            } var fraction = new MyClass (1, 3, ""); Fraction.            Print ();       try {         fraction = new MyClass (1, 2, NULL);                    } catch (ArgumentNullException e) {if (E.paramname = = "Separatorspaces")            WriteLine ("separatorspaces can not is null");            } MyClass v;            MyClass.Dic.TryGetValue ("Harf", out v); V?.            Print (); var a = v?.            A            WriteLine (A = = null); var B = v?            ["B"];            WriteLine (b = = null); WriteLine (v?.            ToString () = = null); WriteLine (New MyStruct ().            ToString ()); WriteLine (Default (MyStruct).        ToString ()); }    }}

c#6.0 new Features