public void MyDog(string s);
 public void MyDog(int i);
 public void MyDog(string s,int i); 

class A
 {
 成员;
 }
class B:A //继承的写法 派生类:基类
 { 
 成员;
 }

 public override DuoTai()
 {
 Console.WriteLine("此处可以重写父类中的'DuoTai'方法");
 }

 public interfa JieKou
 {
 void g(); //接口成员;
 }

 public abstract class PiSaAll
 {
 成员;
 }

 public string MianBing { get; set; }
 public string Shui { get; set; }

class Dog
 {
 public Dog(string s,int i ) //构造函数写法
 {
 Console.WriteLine("这是一只小狗！名叫{0},今年{1}岁",s,i);
 }
 }

 Mian中调用:
 Dog dog = new Dog("铛铛",4);

 1. string conStr = "Data Source=IUCL8V4Y7NW5IRA\\SQLEXPRESS;Initial catalog=BookShopPlus;User Id=sa;Pwd=sa123"; 
 
 2. static string s = @"server=MY-20150918RBSF;database=Beauty;Integrated Security = true"; 
 
 3. static string s = ConfigurationSettings.AppSettings["dbinfo"].ToString(); 

 1. try{}catch{}
 
 2. try{}catch{}finally{}

 3. using(SqlConnection con = new SqlConnection(conStr)){}

 1.using System.Data.SqlClient; ==>用于SQL数据库

 2.using System.Data; ==>可使用Data类

 3.using System.Collections; ==>ArrayList数组 

ArrayList arr = new ArrayList();
 ArrayList arr1 = new ArrayList(30); ==>可以添加到30以上 Student类
 arr.Add(12); ==>定义int类型 　　　　 Class Student  　　　　　　　　　　　　　　　　　　　　 {
 arr.Add(true); ==>定义bool类型 　　 　　public int No { get; set; }  
 arr.Add("Hello"); ==>定义字符串类型 　　　　 public string Name { get; set; }
 Student st = new Student(); ==>实例化Student类 　　}
 st.No = 1001; ==>给st中的No赋值
 st.Name = "zhangsan"; ==>给st中的Name赋值
 arr.Add(st); ==>将st的值添加到arr中
 arr.RemoveAt(1); ==>删除数组中第二个
 arr.Insert(1, "World"); ==>插入数据World
 for (int i = 0; i < arr.Count; i++)
 {
 Console.WriteLine(arr[i]); ==>for循环便利数组
 }

Hashtable ht = new Hashtable();
 ht.Add("0531","济南市");
 ht.Add("0532","青岛市");
 ht.Add("0536","潍坊市");
 ht.Add("0631","威海市"); 
 Console.WriteLine(ht["0531"]); ==>输出下标为0531的值，此处为"济南市";
 Console.WriteLine(ht.Count); ==>输出Hashtable数组的长度,此处为4;

Hashtable ht = new Hashtable();
 ht.Add("0531","济南市");
 ht.Add("0532","青岛市");
 ht.Add("0536","潍坊市");
 ht.Add("0631","威海市"); 
 ICollection keys = ht.Keys; ==>获取Hashtable中所有的keys值,这里不是方法,所以keys后没括号
 foreach(string k in keys)
 {
 Console.WriteLine("{0}-----{1}",k,ht[k]);
 }

Hashtable ht = new Hashtable();
 ht.Add("0531","济南市");
 ht.Add("0532","青岛市");
 ht.Add("0536","潍坊市");
 ht.Add("0631","威海市");
 ICollection keys = ht.Keys; ==>获取Hashtable中所有的keys值,这里不是方法,所以keys后没括号
 IEnumerator ie = keys.GetEnumerator(); ==>返回访问集合的枚举数
 while(ie.MoveNext()) ==>枚举数推进到集合的下一元素 
 {
 Console.WriteLine(ie.Current); ==>获取集合中当前元素
 Console.WriteLine("{0}-----{1}",ie.Current,ht[ie.Current]);
 }

ArrayList arr1 = new ArrayList(); 
 arr.Add(12);  ==>定义int类型    
 arr.Add(true); ==>定义bool类型     arr.Add("Hello"); ==>定义字符串类型  
 　arr.Insert(1,"World"); ==>在第一个后面插入字符串"World"
 IEnumerator ie = keys.GetEnumerator(); ==>返回访问集合的枚举数 
 　　 while(ie.MoveNext()) ==>枚举数推进到集合的下一元素 
 　　 {
 　　Console.WriteLine(ie.Current); ==>获取集合中当前元素
 　　Console.WriteLine("{0}-----{1}",ie.Current,ht[ie.Current]);
 　　 }

定义Student按照学号排序的类:
 class MyStudentCompare:IComparer<Student> ==>定义类型为比较两个对象而实现的方法
 { 
 public int Compare(Student st1, Student st2)
 {
 return st1.No - st2.No;
 }
 }
 定义Student类：
 Class Student
 {
 public int No { get; set; }
   
 public string Name { get; set; }
 }
 定义Student泛型:
 List<Student> list = new List<Student>(); ==>定义Student类型的泛型
 list.Add(new Student(1002, "张三2"));
 list.Add(new Student(1004, "张三4"));
 list.Add(new Student(1003, "张三3"));
 list.Add(new Student(1001, "张三1"));
 list.Add(new Student(1005, "张三5"));
 list.Sort(new MyStudentCompare()); ==>调用定义的类方法
 foreach (Student st in list)
 {
 Console.WriteLine(st.ToString());
 }

LinkedList<int> lnk = new LinkedList<int>(); ==>定义int类型的泛型 
 lnk.AddFirst(1); 
 lnk.AddLast(2); 
 lnk.AddLast(3); 
 foreach (var lnk1 in lnk) ==> var可以识别类型,var本身也是种类型
 {
 Console.WriteLine(lnk1);
 } 
 LinkedListNode<int> first = lnk.First; ==>获取第一个节点 
 Console.WriteLine(first.Value); ==>把第一个节点值输出

 Dictionary<int, string> dic = new Dictionary<int, string>();
 dic.Add(0531, "济南"); 
 dic.Add(0532, "青岛"); 
 ICollection<int> key2 = dic.Keys; ==>获取dic中的键的集合 
 foreach (var k in key2) ==> var 是3.0 新加的功能
 {
 Console.WriteLine("{0}----{1}", k, dic[k]);
 }

HashSet<string> hs = new HashSet<string>(); ==>可添加string类型的数值
 hs.Add("12345"); 
 hs.Add("Apple"); 
 hs.Add("1234"); 
 hs.Add("Hello"); 
 hs.Add("123"); 
 hs.Add("World");
 IEnumerator<string> ie = hs.GetEnumerator();
 while (ie.MoveNext())
 {
 Console.WriteLine(ie.Current);
 }
 Console.WriteLine(hs.Count);

 public class Person <T>
 {
 public T No {get ; set ;}
 }