c#7.0 new Features

SOURCE Reference: Https://docs.microsoft.com/zh-cn/dotnet/csharp/whats-new/csharp-7

"VS2017 Support"

1.out variable (out variables)

Before the out parameter needs to be declared in advance outside the calling method, c#7.0 allows the out parameter to be declared in the method parameter pass.

Old wording:

int num; if (int.) TryParse ("123" out num)) {    Console.WriteLine (num);} Else {    Console.WriteLine ("Could not parse! " );}

New wording:

if (int.) TryParse ("123"outint  num)) {    Console.WriteLine (num);} Else {    Console.WriteLine ("Could not parse! " );}

Out parameter declaration in method supports VAR implicit type

2. Tuples (tuples)

A method with multiple return types is worth the solution, using tuples.

Old wording:

Static voidMain (string[] args) {    vardata =Getfullname (); Console.WriteLine (data.    ITEM1); Console.WriteLine (data.    ITEM2); Console.WriteLine (data. ITEM3);}Statictuple<string,string,string>Getfullname () {return Newtuple<string,string,string> ("a","b","C");}

New wording:[need to get System.valuetuple's reference via Nutget]

Static voidMain (string[] args) {    vardata =GetFullName1 ();    Console.WriteLine (DATA.A);    Console.WriteLine (DATA.B); Console.WriteLine (DATA.C);}Static(stringAstringBstringc) GetFullName1 () {return("a","b","C");}

Deconstructed tuples Get return Values (multiple):

Static voidMain (string[] args) {    //use Var to define a destructor tuple(stringAstringBstringc) =GetFullName1 ();    Console.WriteLine (a);    Console.WriteLine (b); Console.WriteLine (c);}Static(stringAstringBstringc) GetFullName1 () {return("a","b","C");}

3.pattern matching (matching mode)

Assign a value directly when judging the type.

Old wording:

Object 1 ; if  is int // is judgment {    int num1 = (int// split    intTen // Add ten    // Output }

New wording:[consider using this notation when using reflection]

Object 1 ; if  is int num1)// to determine that obj is of type int, directly assigned to NUM1    {int;     // Output }

New gameplay for switch:

Static DynamicADD (Objecta) {    Dynamicdata; Switch(a) { Case intB:data= b++;  Break;  Case stringC:data= C +"AAA";  Break; default: Data=NULL;  Break; }    returndata;}

c#7.0 new Features