C#傳值、輸出、引用、數(shù)組、具名、可選參數(shù),擴(kuò)展方法

1、值參數(shù)聲明時(shí)不帶修飾符的形參是值形參。一個(gè)值形參對(duì)應(yīng)一個(gè)局部變量，只是它的初 始值來自于該方法調(diào)用所提供的相應(yīng)實(shí)參。快速替換變量Alt + Enterusing System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ParametersExampleclass Programstatic void Main(string args)Student Oldstu = new Student() Name = Tim ;So

2、meMethod(Oldstu);Console.WriteLine(0, 1, Oldstu.GetHashCode(),Oldstu.Name);static void SomeMethod(Student stu)stu = new Student() Name = Tom ;Console.WriteLine(0, 1, stu.GetHashCode(), stu.Name);class Studentpublic string Name get; set; using System;using System.Collections.Generic;using System.Linq

3、;using System.Text;using System.Threading.Tasks;namespace ParametersExampleclass Programstatic void Main(string args)Student stu = new Student() Name = Tim;UpdateObject(stu);Console.WriteLine(0, 1, stu.GetHashCode(), stu.Name);static void UpdateObject(Student stu)stu.Name = Tom;/ 副作用，side-effectCons

4、ole.WriteLine(0, 1, stu.GetHashCode(), stu.Name);class Studentpublic string Name get; set; 引用參數(shù)引用形參是用ref修飾符聲明的實(shí)參，引用形參并不創(chuàng)建新的存儲(chǔ)位置。引用形 參表示的存儲(chǔ)位置恰是在方法調(diào)用中作為實(shí)參給出的那個(gè)變量所表示的存儲(chǔ)位 置。變量在可以作為引用形參之前，必須先明確輔助。注意：引用參數(shù)并不創(chuàng)建變量的副本使用ref修飾符顯示指出一一此方法的副作用是改變實(shí)際參數(shù)的值using System;using System.Collections.Generic;using System.Linq

5、;using System.Text;using System.Threading.Tasks;namespace ParametersExample class Program static void 5如 args)int y = 1;IWantSideEffect(ref y);static void IWantSideEffect(ref int x)/x*引用參數(shù)-引用類型，創(chuàng)建新對(duì)象using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Thread

6、ing.Tasks;namespace ParametersExampleclass Programstatic void Main(string args)Student outterStu = new Student() Name = Tim ;Console.WriteLine(HashCode=0, Name=1, outterStu.GetHashCode(), outterStu.Name);Console.WriteLine();IWantSideEffect(ref outterStu);Console.WriteLine(HashCode=0, Name=1, outterS

7、tu.GetHashCode(), outterStu.Name);static void IWantSideEffect(ref Student stu)stu = new Student() Name = Tom ;Console.WriteLine(HashCode=0, Name=1, stu.GetHashCode(),stu.Name);class Student岫 string g 5引用參數(shù)-引用類型，不創(chuàng)建新對(duì)象只改變對(duì)象值此時(shí)與傳值參數(shù)去掉(ref)在效果上并無不同，但機(jī)理不一樣；前者的outterStu stu指針一致，后者為指針的指針一致using System;usi

8、ng System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ParametersExampleclass Programstatic void Main(string args)Student outterStu = new Student() Name = Tim ;Console.WriteLine(HashCode=0, Name=1,outterStu.GetHashCode(), outterStu.Name);Console.Writ

9、eLine();IWantSideEffect(ref outterStu);Console.WriteLine(HashCode=0, Name=1,outterStu.GetHashCode(), outterStu.Name);static void IWantSideEffect(ref Student stu)stu.Name = Tom;Console.WriteLine(HashCode=0, Name=1,stu.GetHashCode(),stu.Name);class Studentpublic string Name get; set; 輸出形參用out修飾符聲明的形參；

10、輸出形參不需要?jiǎng)?chuàng)建新的存儲(chǔ)位置；變量在可以作為 輸出形參傳遞之前不一定需要明確賦值；在方法返回之前，該方法的每個(gè)輸出形 參都必須明確賦值；注意：輸出參數(shù)并不創(chuàng)建變量的副本方法體內(nèi)必需要有對(duì)輸出變量的賦值的操作用Out修飾符顯示指出一一此方法的副作用是通過參數(shù)向外輸出值從語義上講一一ref是為了 “改變”，out是為了 “輸出”輸出參數(shù)一一值類型using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace Parame

11、tersExampleclass Programstatic void Main(string args)Console.WriteLine(Please inout first number:);string arg1 = Console.ReadLine();double x = 0;bool b1 = double.TryParse(arg1, out x);if(b1 = false)Console.WriteLine(Input error!);return;Console.WriteLine(Please inout second number:);string arg2 = Co

12、nsole.ReadLine();double y = 0;bool b2 = double.TryParse(arg2, out y);if (b2 = false)Console.WriteLine(Input error!);return;double z = x + y;Console.WriteLine(0 + 1 = 2”, x, y, z);using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace

13、ParametersExampleclass Programstatic void Main(string args)f x = 100；bool b = DoubleParser.TryParse(ABC”, out x);:(b=true)_+1);elseerb_ i_tryResult = doub5catch板t=0;/”輸出類型一一引用類型using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace Pa

14、rametersExampleclass Programstatic void Main(string args)Student stu = null;bool b = StudentFactory.Create(Tim”, 34, out stu);if (b = true)Console.WriteLine(Student 0, age is 1.”, stu.Name, stu.Age);class Studentpublic int Age get; set; public string Name get; set; class StudentFactorypublic static

15、bool Create(string stuName, int stuAge, out Student result)result = null;if(string.IsNullOrEmpty(stuName)return false;if(stuAge80)return false;_,心5數(shù)組參數(shù)必需是形參列表中的最后一個(gè)，由params修飾舉例：String.Format 方法和 String.Split 方法using System;using System.Collections.Generic;using System.Linq;using System.Text;using Sy

16、stem.Threading.Tasks;namespace ParametersExampleclass Programstatic void Main(string args)int result = CalculateSum(1, 2, 3);：_ 5)int sum = 0;一,5廣+=-，廣；using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ParametersExample( class Pr

17、ogram1 M void 55,(s.string result = str.Split(;, ., ,);i(n”具名參數(shù)參數(shù)的位置不再受約束提高代碼可讀性u(píng)sing System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ParametersExampleclass Program static void gs)P_ );g Prage)enam可選參數(shù)參數(shù)因?yàn)榫哂心J(rèn)值而變得“可選”不推薦使用可選參數(shù)using S

18、ystem;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ParametersExampleclass Program static 用 5傾 args)PrinfInfo();static void PrinfInfo(string name = Tim, int age = 34)Ceige)擴(kuò)展方法(this參數(shù))方法必需是公有的、靜態(tài)的，即被public static所修飾必需是形參列表中的第一個(gè)，由this修飾必需由一個(gè)靜態(tài)類(一般類名為SomeTypeExtension)來統(tǒng)一收納對(duì)SomeType類型的擴(kuò)展方法舉例：LINQ方法using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Task