C#基础概念 代码样例

C# int与string一起操作时注意

1 int a1= 1;
2 string a2= "2";
3 Console.WriteLine(a1+a2);
4 Console.ReadKey();
5 //在和string一起操作时，C#会把int转换为string，来实现两个string之间的连接，结果是12，不是3

C# 运算符重载

 namespace 运算符重载{

     class Program
     {
         public int Value { get; set; }
         static void Main(string[] args)
         {
             // 运算符重载
             ///若要在自定义类中重载运算符，您需要在该类中创建具有正确签名的方法。
             /// 该方法必须命名为“operator X”，其中 X 是正在重载的运算符的名称或符号。
             /// 一元运算符具有一个参数，二元运算符具有两个参数。
             /// 在每种情况下，参数的类型必须与声明该运算符的类或结构的类型相同
             /// public static Complex operator +(Complex c1, Complex c2)

             Program t1 = new Program();
             t1.Value = ;
             Program t2 = new Program();
             t2.Value = ;
             Program t3 = t1 * t2;
             Console.WriteLine(t3.Value);
             Console.ReadKey();

         }

         public static Program operator * (Program p1,Program p2)
         {
             Program t1 = new Program();
             t1.Value = p1.Value + p2.Value;
             return t1;
         }
     }
 }

Lambda表达式

 namespace Lambda
 {

     class Program
     {
         delegate void dl();
         static void Main(string[] args)
         {
             //lambda表达式
             dl d = delegate () { Console.WriteLine("this is a test"); };
             d();
             dl d1 = () => Console.WriteLine("where am i?");
             d1();
             dl d2 = () => { Console.WriteLine("what you say"); Console.WriteLine("Are you Sure?"); };
             d2();
             Console.ReadKey();
          }
     }
 }

File方法练习

 namespace File类方法练习
 {

     class Program
     {

         static void Main(string[] args)
         {

             string FilePath = @"e:\\11.txt";
             string FileNewPath = @"e:\\22.txt";

             //写文件
             File.WriteAllText(FilePath, "this is a test for file function");
             //读文件
             string data = File.ReadAllText(FilePath);
             Console.WriteLine(data);
             //复制文件
             File.Copy(FilePath, FileNewPath);
             //删除文件
             File.Delete(FilePath);

             Console.ReadKey();

         }
     }

 }

匿名类型 匿名方法 Anonymous Type

 namespace 匿名类型匿名方法Anonymous_Type
 {
     delegate void Speak(string a);
     class Program
     {
         static void Main(string[] args)
         {
             //匿名类型
             var n = new {name = "school",age=};
             Console.WriteLine(n.name);
             Console.WriteLine(n.age);
             //匿名方法
             Speak ss = delegate (string b) {  Console.WriteLine("this is the string {0}", b); };
             ss("what do you want?");
             Console.ReadKey();

         }
     }
 }

C# 99乘法表

 namespace 乘法表
 {
     class Program
     {
         static void Main(string[] args)
         {
         //99乘法表的程序
         int[] num = new int[];
         for (int i = ; i < ; i++)
         {
             num[i] = i;
         }
         Console.ForegroundColor = ConsoleColor.Red;
         for (int i = ; i < ; i++)
         {
             for (int j = ; j < i; j++)
             {

                 Console.Write("{0}X{1}={2}  ", num[i], num[j], num[i] * num[j]);
                 if (num[i] * num[j] < )
                 {
                     Console.Write(" ");
                 }

             }
             Console.WriteLine();
         }
         Console.ReadKey();

     }
 }
 }

C# 运算符重载Operator使用

 namespace  Operator运算符重载
     class Speak
     {
         public string   _name;
         public Speak(string a)
         {
             this._name = a;
         }
         public static Speak operator * (Speak a1,Speak a2)
         {
             return new Speak ( a1._name + a2._name );
         }
     }

     class Program
     {
         static void Main(string[] args)
         {
             Speak s1 = new Speak("jingya");
             Speak s2 = new Speak("dongbao");
             Speak s3 = s1 * s2;
             Console.WriteLine(s3._name);
             Console.ReadKey();
         }
     }
 }

C# linq简单用法

 namespace LINQ简单用法
 {

     class girl
     {
         public string _name { get; set; }
         public int _age;
     }

     class Program
     {
         static girl[] cc = new girl[]
 {
        new girl {_name = "小明",_age =  },
       new girl {_name = "小东",_age = },
       new girl {_name = "小丽",_age =  }

 };

         static void Main(string[] args)
         {
             string[] ss = { "this is a very things" ,"inga","jiaoofdjaoisdjfoia","kjadofjasing"};

             var query = from p in ss where p.Contains("ver") select p;
             foreach (var item in query)
             {
                 Console.WriteLine(item);
             }
             var query2 = from pp in cc where pp._age <  select pp;
             foreach (var item in query2)
             {
                 Console.WriteLine(item._name);
             }
             Console.ReadKey();
         }
     }
 }

C# 委托与事件

 namespace 委托与事件
 {
     delegate string CompareEventHandler(int num1,int num2);

     class Program
     {
         static void Main(string[] args)
         {

             CompareEventHandler dd = CompareFunction.Compare;
             //注册事件
             EventClass ccc = new EventClass();
             ccc.CompareEvent +=dd;
             ccc.CC(,);
             Console.ReadKey();
         }

     }
     class CompareFunction
     {
         public static string Compare(int i ,int j )
         {
             if (i > j)
             {
                 return "前面的大";
             }
             else
             {
                 return "后面的大";
             }
         }
     }
     class EventClass
     {
         public event CompareEventHandler CompareEvent;
         public void CC(int i ,int j )
         {
             if(CompareEvent != null)
            {
                 Console.WriteLine(CompareEvent(i,j));
             }
             else
             {
                 Console.WriteLine("The Event is over!");
             }
         }

     }

 }

C# Enum遍历

 1 namespace Enum遍历
 2 {
 3     enum aa { a = 1, b = 2,c= 3};
 4     class Program
 5     {
 6         static void Main(string[] args)
 7         {
 8             foreach (var a  in Enum.GetValues(typeof(aa)))
 9             {
10                 string s = $" {a} ";
11                 Console.WriteLine(s);
12             }
13             //上面输出的是  a  b  c
14             foreach (int a in Enum.GetValues(typeof(aa)))
15             {
16                 string s = $" {a} ";
17                 Console.WriteLine(s);
18             }
19             //上面这段代码输出的是 1  2   3
20             //感觉这个可能是枚举类型的一个方法，虽然Enum.GetValues返回的是一个数组，但是这个数组
21             //是string类型数组，还是int类型数组，是有var  或者int决定的
22             Console.ReadKey();
23         }
24     }
25 }

C# 迭代器中IEnumerator \ IEnumerable \ Getnumerator的使用

 1 namespace IEnumerable用法
 2 {
 3
 4     class Program
 5     {
 6         static void Main(string[] args)
 7         {
 8             stack aa = new stack();
 9             foreach (var item in aa)
10             {
11                 Console.WriteLine(item);
12             }
13             Console.WriteLine();
14             Console.ReadKey();
15         }
16     }
17     //下面的例子是普通的类继承IEnumerable接口，用yield return返回一个枚举类型
18     public class stack : IEnumerable
19     {
20         string[] ss = { "GG", "dd", "xx", "abc" };
21         public IEnumerator GetEnumerator()
22         {
23             for (int i  = 0; i  < ss.Length; i ++)
24             {
25                 yield return ss[i];
26
27             }
28         }
29     }
30 }

C# 中标准事件、委托EventHandler、参数类EventArgs用法

 namespace 标准事件用法
 {
     class Program
     {
         static void Main(string[] args)
         {
             Bank jianhang = new Bank("建设银行",);
             People dong = new People("", jianhang);
             jianhang.PlayByCard();
             Console.WriteLine();
             Console.ReadKey();
         }
     }
     public class CarEventArgs : EventArgs
     {
         private string _name;
         private int _amount;
         private int _yue;
         public int Yue
         {
             set { _yue = value; }
             get { return _yue; }
         }
         public string Name
         {
             set { _name = value; }
             get { return _name; }
         }
         public int Amount
         {
             set { _amount = value; }
             get { return _amount; }
         }

     }
     class Bank
     {
         public string BankName { set; get; }
         public int Balance { set; get; }
         public Bank(string s ,int i )
         {
             this.BankName = s;
             this.Balance = i;
         }

         public event EventHandler<CarEventArgs> MyEvent;

         public void PlayByCard(int i)
         {
             CarEventArgs cc = new CarEventArgs();
             cc.Amount = i;
             cc.Yue = this.Balance - i;
             cc.Name = this.BankName;
             if (MyEvent != null)
             {
                 MyEvent(this,cc); //调用事件只能在其中加Object和EventArgs
             }
             else
             {
                 Console.WriteLine("系统故障，请紧急联系客服看看你的钱还有没有！");
             }
         }
     }
     class People
     {
         public string id;
         public People(string ID,Bank bb)
         {
             this.id = ID;
             bb.MyEvent += Paycard; //通过匿名方法，将方法给EventHandler委托，再给事件
         }
         private void Paycard(object o ,CarEventArgs e)
         {

             Console.WriteLine( $"尊敬的{id},您好，您从{e.Name}银行消费了{e.Amount}元，余额为{e.Yue}");
         }
     }
 }

C# 属性SET GET前的访问修饰符

         private string _name;
         public string Name
         {
             protected set { _name = value; }
             private get { return _name; }
             //属性SET、GET上的访问修饰符默认是跟属性前面的修饰符一样，
             //如果非要在get或者set上加访问修饰符，就要比前面的属性上的访问修饰符“小”
         }

C# 类中的无限循环

 namespace 类中的无限循环
 {
     class Mytest
     {
         private int i = ;
         public void Speak()
         {
             Mytest ss = new Mytest();
             {
                 if (i < ) { Speak(); }

             }
             Console.WriteLine("this is a test!");
             i--;
         }
     }
     class Program
     {
         static void Main(string[] args)
         {
             Mytest aa = new Mytest();

                 aa.Speak();
                 aa.Speak();
                 aa.Speak();
                 aa.Speak();
                 aa.Speak();
                 aa.Speak();
                 aa.Speak();
                 aa.Speak();
                 aa.Speak();
                 aa.Speak();
                 aa.Speak();  

         }
     }
 }