C#经典面试题及答案

心已赠人 2021-11-01 23:02 448阅读 0赞

1：委托和事件

![None.gif][]   // 事件类   
![None.gif][]      public   class  EventClass  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]     ![dot.gif][] \{  
![InBlock.gif][]        public void display(object sender, System.EventArgs e)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            Console.WriteLine("This is the Event Class");  
![InBlock.gif][]            Console.ReadLine();  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}   
![None.gif][]     // 调用类   
![None.gif][]      class  InvokeClass  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]     ![dot.gif][] \{  
![InBlock.gif][]        //声明代理对象,注意参数  
![InBlock.gif][]        public delegate void delegateobj(object sender, System.EventArgs e);  
![InBlock.gif][]        //声明事件对象   
![InBlock.gif][]        private event delegateobj obj;  
![InBlock.gif][]        //声明要调用的事件类对象  
![InBlock.gif][]        private EventClass ec;  
![InBlock.gif][]  
![InBlock.gif][]        public InvokeClass()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            ec = new EventClass();  
![InBlock.gif][]            //添加事件对象到事件队列中，参数为要调用的事件  
![InBlock.gif][]            this.obj \+= new delegateobj(ec.display);  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]        //调用delegate对象触发事件  
![InBlock.gif][]        protected void OnObj(System.EventArgs e)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            if (this.obj != null)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]            ![dot.gif][]\{  
![InBlock.gif][]                obj(this, e);  
![ExpandedSubBlockEnd.gif][]            \}  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]        public void RaiseEvent()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            EventArgs e = new EventArgs();  
![InBlock.gif][]            OnObj(e);  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]        static void Main(string\[\] args)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            InvokeClass ic = new InvokeClass();  
![InBlock.gif][]            Console.WriteLine("Please input a string");  
![InBlock.gif][]            string input = Console.ReadLine();  
![InBlock.gif][]            if (input.Equals(""))  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]            ![dot.gif][]\{  
![InBlock.gif][]                Console.WriteLine("Sorry,you don't input anything");  
![ExpandedSubBlockEnd.gif][]            \}  
![InBlock.gif][]            else  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]            ![dot.gif][]\{  
![InBlock.gif][]                //触发事件  
![InBlock.gif][]                ic.RaiseEvent();  
![ExpandedSubBlockEnd.gif][]            \}  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}

2:遍历页面中所有的TextBox,交将值设置成"a"

![None.gif][] for  ( int  j  =   0 ; j  <   this .Controls.Count; j \++ ) 
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]             ![dot.gif][] \{ 
![InBlock.gif][]                foreach (object o in Page.Controls\[j\].Controls) 
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]                ![dot.gif][]\{ 
![InBlock.gif][]                    
![InBlock.gif][]                    if (o is TextBox) 
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]                    ![dot.gif][]\{ 
![InBlock.gif][]                        TextBox txt = (System.Web.UI.WebControls.TextBox)o; 
![InBlock.gif][]                        txt.Text = "A"; 
![ExpandedSubBlockEnd.gif][]                    \} 
![InBlock.gif][]                    
![ExpandedSubBlockEnd.gif][]                \} 
![ExpandedBlockEnd.gif][]            \}

3：常用排序算法

![ExpandedBlockStart.gif][] ![ContractedBlock.gif][]   /\*\*/ /// <summary> 
![InBlock.gif][]        /// /冒泡排序 
![ExpandedBlockEnd.gif][]        /// </summary> 
![None.gif][]          private   void  BubbleSort() 
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]         ![dot.gif][] \{ 
![InBlock.gif][]            //冒泡排序 
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]            int\[\] list = new int\[5\] ![dot.gif][]\{ 111, 12, 223, 854, \-5655 \};//初始化数组 
![InBlock.gif][]            int i, j, temp; 
![InBlock.gif][]            for (j = 1; j < list.Length; j\++) 
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]            ![dot.gif][]\{ 
![InBlock.gif][]                for (i = 0; i < list.Length \- j; i\++) 
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]                ![dot.gif][]\{ 
![InBlock.gif][]                    if (list\[i\] > list\[i \+ 1\]) 
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]                    ![dot.gif][]\{ 
![InBlock.gif][]                        temp = list\[i\]; 
![InBlock.gif][]                        list\[i\] = list\[i \+ 1\]; 
![InBlock.gif][]                        list\[i \+ 1\] = temp; 
![ExpandedSubBlockEnd.gif][]                    \} 
![ExpandedSubBlockEnd.gif][]                \} 
![InBlock.gif][] 
![ExpandedSubBlockEnd.gif][]            \} 
![InBlock.gif][]             
![InBlock.gif][] 
![ExpandedBlockEnd.gif][]        \} 
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]         /\*\*/ /// <summary> 
![InBlock.gif][]        /// 选择排序 
![ExpandedBlockEnd.gif][]        /// </summary> 
![None.gif][]          private   void  SelectSort() 
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]         ![dot.gif][] \{ 
![InBlock.gif][]            //选择排序 
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]            int\[\] a = new int\[5\] ![dot.gif][]\{ 111, 12, 223, 854, \-5655 \};//初始化数组 
![InBlock.gif][]            int min, min\_k;//定义最小数,和最小数的下标 
![InBlock.gif][]            for (int i = 0; i < 5; i\++) 
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]            ![dot.gif][]\{ 
![InBlock.gif][]                min = a\[i\];//将当前循环的数设置成最小数 
![InBlock.gif][]                min\_k = i; 
![InBlock.gif][]                for (int j = i \+ 1; j < 5; j\++) 
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]                ![dot.gif][]\{ 
![InBlock.gif][] 
![InBlock.gif][]                    if (a\[j\] < min) 
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]                    ![dot.gif][]\{ 
![InBlock.gif][]                        min = a\[j\]; 
![InBlock.gif][]                        min\_k = j; 
![InBlock.gif][]                        int tem = a\[min\_k\]; 
![InBlock.gif][]                        a\[min\_k\] = a\[i\]; 
![InBlock.gif][]                        a\[i\] = tem; 
![InBlock.gif][] 
![InBlock.gif][] 
![ExpandedSubBlockEnd.gif][]                    \} 
![InBlock.gif][] 
![InBlock.gif][] 
![ExpandedSubBlockEnd.gif][]                \} 
![InBlock.gif][] 
![InBlock.gif][] 
![ExpandedSubBlockEnd.gif][]            \} 
![InBlock.gif][] 
![ExpandedBlockEnd.gif][]        \}

4: 结构体(Struct) 和 类（Class）

对于结构和类，初看上去都一样。都可以有自己的字段，属性，方法，还能有构造函数。但是这两者其实有很大的不同，而且各自有各自的应用范围。下面还是谈谈两者的分别吧。 
 
      <1> 结构的特点和性能优势 
 
      结构是值类型，继承自System.ValueType。结构相对于类来说有两个性能上的优势，结构通常分配在栈（Stack）上面，类的实际内容通常分配在堆（Heap）上面，访问栈的速度会比访问堆的速度更快。但是这并不是一个明显的优势。最主要的是栈上面的内容释放是非常快的，通常在函数调用结束以后，栈就自动释放了；但是对于堆来说，必须等待垃圾收集器（Garbage Collector）来收集，往往垃圾收集器的工作都有滞后特性，所以我们不一定当时就能注意到性能的变化，但是这种影响终究会体现出来。 
 
      <2> 结构的弱点 
 
       （1）作为参数传递的时候效率低 
 
        （2）装箱（Boxing）和解箱（Unboxing）效率低

<3>  何时使用结构，何时使用类？ 
 
    在下面的情况下使用类 
 
      1 内容很多的时候，因为结构总是暗地里拷贝了一个临时变量。 
      2 需要非常多内存的时候，因为栈的容量有限，而堆通常是足够使用的。 
      3 需要在声明字段的时候进行初始化。 
      4 需要从基类继承。 
      5 需要多态性。接口也可以用来实现多态性，但是因为结构是值类型，尽管它可以从接口继承，但是在多态过程中会进行装箱和解箱的操作。

**在下面的情况下使用结构**  
  
       1 希望能够象原始类型（比如int，double之类的）一样使用它。比如我们可以声明一个复数结构，然后像double类型一样地使用它。  
      2 需要的内存较少，栈可以完全地容纳它。  
      3 想避开垃圾收集器的处理，自己掌握资源的释放。  
      4 只需要缺省的值，而不需要在声明字段的时候赋值。  
      5 不需要从基类继承，当然，不包括ValueType。  
      6 不需要多态行为。  
  
      5:给XML文件中已知的结点添加属性:  
  
         XML文件结构如下：

![None.gif][] <? xml version = " 1.0 "  encoding = " utf-8 " ?> 
![None.gif][] < MovieBlacklist > 
![None.gif][]   < Blacklist id = " 17050 "  part = " 32 "  name = " 江湖俏佳人 "  age = " 20 "   /> 
![None.gif][]   < Blacklist id = " 17310 "  part = " 1 "  name = " 阴谋 "   /> 
![None.gif][]   < Blacklist id = " 17316 "  part = " 1 "  name = " WWE摔角080314 "   /> 
![None.gif][]   < Blacklist id = " 17190 "  part = " 1 "  name = " 2012世界末日 "   /> 
![None.gif][] </ MovieBlacklist >

给第一个Blacklist添加属性age

![ExpandedBlockStart.gif][] ![ContractedBlock.gif][] /\*\*/ /// <summary> 
![InBlock.gif][]          /// 给已知结点增加一个属性 
![InBlock.gif][]          /// </summary> 
![InBlock.gif][]          /// <param name="XmlPathNode"></param> 
![ExpandedBlockEnd.gif][]          /// <param name="Content"></param> 
![None.gif][]          public   void  XMLAddAttributes( string  XmlPathNode, string  sName,  string  sContent) 
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]           ![dot.gif][] \{ 
![InBlock.gif][]              // 创建节点 
![InBlock.gif][]              XmlNode attrCount = objXmlDoc.CreateNode(XmlNodeType.Attribute, sName , null); 
![InBlock.gif][]              attrCount.Value = sContent ; 
![InBlock.gif][]              // 添加节点属性 
![InBlock.gif][]              objXmlDoc.SelectSingleNode(XmlPathNode).Attributes.SetNamedItem(attrCount); 
![ExpandedBlockEnd.gif][]          \}

**6.求以下表达式的值，写出您想到的一种或几种实现方法： 1-2+3-4+……+m**   
答：

int  sum = 0 ; 
 bool  flag = true ; 
 for ( int  i = 1 ;i <= m;i \++ ) 
\{ 
    if (flag) 
      sum \+= i; 
    else 
      sum \-= i; 
   flag =! flag; 
\} 
 return  sum;

**7. 一列数的规则如下: 1、1、2、3、5、8、13、21、34...... 求第30位数是多少， 用递归算法实现。**    
答：

public   class  MainClass 
                  \{ 
                   public   static   void  Main() 
                  \{ 
                  Console.WriteLine(Foo( 30 )); 
                  \} 
                   public   static   int  Foo( int  i) 
                  \{ 
                   if  (i  <=   0 ) 
                   return   0 ; 
                   else   if (i  >   0   &&  i  <=   2 ) 
                   return   1 ; 
                   else   return  Foo(i  \- 1 )  \+  Foo(i  \-   2 ); 
                  \} 
                  \}

**8.在下面的例子里**

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][] Code   
![None.gif][]class Program  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        static void Main(string\[\] args)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            B \_b = new B();  
![InBlock.gif][]            Console.ReadKey();  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}  
![None.gif][]    class A  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        public A()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            PrintFields();  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        public virtual void PrintFields() ![dot.gif][]\{ \}  
![ExpandedBlockEnd.gif][]    \}  
![None.gif][]    class B : A  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        int x = 1;  
![InBlock.gif][]        int y;  
![InBlock.gif][]        public B()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            y = \-1;  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]        public override void PrintFields()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            Console.WriteLine("x=\{0\},y=\{1\}", x, y);  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}

当使用new B()创建B的实例时，产生什么输出？  
答： X=1,Y=0       
  
      **9.short s1 = 1; s1 = s1 + 1;有什么错? short s1 = 1; s1 += 1;有什么错?**  
  
答：short s1 = 1; s1 = s1 + 1;有错，s1是short型，s1+1是int型,不能显式转化为short型。可修改为s1 =(short)(s1 + 1) 。short s1 = 1; s1 += 1正确。  
           
    **10.写出输出结果**

![None.gif][] public   abstract   class  A  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]     ![dot.gif][] \{  
![InBlock.gif][]        public A()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            Console.WriteLine('A');  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]        public virtual void Fun()    
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]       ![dot.gif][]\{  
![InBlock.gif][]            Console.WriteLine("A.Fun()");  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}   
![None.gif][]  
![None.gif][]     public   class  B : A  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]     ![dot.gif][] \{  
![InBlock.gif][]        public B()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            Console.WriteLine('B');  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]  
![InBlock.gif][]        public new void Fun()    
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]       ![dot.gif][]\{  
![InBlock.gif][]            Console.WriteLine("B.Fun()");  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]  
![InBlock.gif][]        public static void Main()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            A a = new B();  
![InBlock.gif][]            a.Fun();  
![InBlock.gif][]            Console.ReadKey();  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}

A  
B  
A.Fun()  
        第一:调用父类构造函数,第二:调用自身构造函数.  
  
         **11.写出输出结果**

![None.gif][] public   class  A  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]     ![dot.gif][] \{  
![InBlock.gif][]        public virtual void Fun1(int i)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            Console.WriteLine(i);  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]  
![InBlock.gif][]        public void Fun2(A a)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            a.Fun1(1);  
![InBlock.gif][]            Fun1(5);  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}   
![None.gif][]  
![None.gif][]  
![None.gif][]     public   class  B : A  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]     ![dot.gif][] \{  
![InBlock.gif][]        public override void Fun1(int i)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            base.Fun1(i \+ 1);  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]  
![InBlock.gif][]        public static void Main()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            B b = new B();  
![InBlock.gif][]            A a = new A();  
![InBlock.gif][]            a.Fun2(b);  
![InBlock.gif][]            b.Fun2(a);  
![InBlock.gif][]            Console.ReadKey();  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}

2  
    5  
    1

**12:写一个HTML页面，实现以下功能，左键点击页面时显示“您好”，右键点击时显示“禁止右键”。并在2分钟后自动关闭页面。** 
 
答：<script \*\*\*script>

setTimeout( ' window.close(); ' , 3000 ); 
function show() 
\{ 
 if  (window. event .button  ==   1 ) 
\{ 
alert( " 左 " ); 
\} 
 else   if  (window. event .button  ==   2 ) 
\{ 
alert( " 右 " ); 
\} 
\} 
 </ script >

**13:大概描述一下ASP。NET服务器控件的生命周期**

答：初始化 加载视图状态 处理回发数据 加载 发送回发更改通知 处理回发事件 预呈现 保存状态 呈现 处置 卸载

**14:程序设计:**猫大叫一声，所有的老鼠都开始逃跑，主人被惊醒。(C\#语言)

要求：  1.要有联动性，老鼠和主人的行为是被动的。

2.考虑可扩展性，猫的叫声可能引起其他联动效应。

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][] Code   
![None.gif][]public interface Observer  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        void Response();    //观察者的响应，如是老鼠见到猫的反映  
![ExpandedBlockEnd.gif][]    \}  
![None.gif][]    public interface Subject  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        void AimAt(Observer obs);  //针对哪些观察者，这里指猫的要扑捉的对象---老鼠  
![ExpandedBlockEnd.gif][]    \}  
![None.gif][]    public class Mouse : Observer  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        private string name;  
![InBlock.gif][]        public Mouse(string name, Subject subj)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{             
![InBlock.gif][]            this.name = name;  
![InBlock.gif][]            subj.AimAt(this);  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]          
![InBlock.gif][]        public void Response()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            Console.WriteLine(name \+ " attempt to escape!";  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}  
![None.gif][]    public class Master : Observer  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]    ![dot.gif][]\{     
![InBlock.gif][]        public Master(Subject subj)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{             
![InBlock.gif][]            subj.AimAt(this);  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]          
![InBlock.gif][]        public void Response()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            Console.WriteLine("Host waken!";  
![ExpandedSubBlockEnd.gif][]        \}    
![ExpandedBlockEnd.gif][]    \}  
![None.gif][]   
![None.gif][]    public class Cat : Subject  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        private ArrayList observers;  
![InBlock.gif][]        public Cat()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{     
![InBlock.gif][]            this.observers = new ArrayList();  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]        public void AimAt(Observer obs)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            this.observers.Add(obs);  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]        public void Cry()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            Console.WriteLine("Cat cryed!";  
![InBlock.gif][]            foreach (Observer obs in this.observers)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]            ![dot.gif][]\{  
![InBlock.gif][]                obs.Response();  
![ExpandedSubBlockEnd.gif][]            \}  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}  
![None.gif][]    class MainClass  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]    ![dot.gif][]\{         
![InBlock.gif][]        static void Main(string\[\] args)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            Cat cat = new Cat();  
![InBlock.gif][]            Mouse mouse1 = new Mouse("mouse1", cat);  
![InBlock.gif][]            Mouse mouse2 = new Mouse("mouse2", cat);  
![InBlock.gif][]            Master master = new Master(cat);  
![InBlock.gif][]            cat.Cry();  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}  
![None.gif][]

下面的程序运行后:

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][] Code   
![None.gif][]class Program  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        static void Main(string\[\] args)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            Class1 o1 = new Class1();  
![InBlock.gif][]            Class1 o2 = new Class1();  
![InBlock.gif][]              
![InBlock.gif][]  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}  
![None.gif][]    class Class1  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        private static int count = 0;  
![InBlock.gif][]        static Class1()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            count\++;  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]        public Class1()  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            count\++;  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedBlockEnd.gif][]    \}

请问，o1.Count的值是多少？( C )

A.1         B.2             C.3             D.4

解答:class1在实例化的时候,先运行静态构造函数,然后运行实例构造函数,第二次实例化的时候,由于静态构造函数已经存在,所有直接实例化,它们都共享静态变量count.

<table style="border-collapse:collapse;"> 
 <tbody> 
 <tr> 
 <td style="width:216pt;" colspan="4">（1）用于对静态字段、只读字段等的初始化。</td> 
 <td style="width:54pt;">　</td> 
 <td style="width:54pt;">　</td> 
 <td style="width:54pt;">　</td> 
 <td style="width:54pt;">　</td> 
 <td style="width:54pt;">　</td> 
 <td style="width:54pt;">　</td> 
 <td style="width:54pt;">　</td> 
 </tr> 
 <tr> 
 <td colspan="7">（2）添加static关键字，不能添加访问修饰符，因为静态构造函数都是私有的。</td> 
 <td>　</td> 
 <td>　</td> 
 <td>　</td> 
 <td>　</td> 
 </tr> 
 <tr> 
 <td colspan="11">（3）类的静态构造函数在给定应用程序域中至多执行一次：只有创建类的实例或者引用类的任何静态成员才激发静态构造函数</td> 
 </tr> 
 <tr> 
 <td colspan="5">（4）静态构造函数是不可继承的，而且不能被直接调用。</td> 
 <td>　</td> 
 <td>　</td> 
 <td>　</td> 
 <td>　</td> 
 <td>　</td> 
 <td>　</td> 
 </tr> 
 <tr> 
 <td colspan="9">（5）如果类中包含用来开始执行的 Main 方法，则该类的静态构造函数将在调用 Main 方法之前执行。</td> 
 <td>　</td> 
 <td>　</td> 
 </tr> 
 <tr> 
 <td colspan="10">&nbsp;&nbsp;&nbsp; 任何带有初始值设定项的静态字段，则在执行该类的静态构造函数时，先要按照文本顺序执行那些初始值设定项。</td> 
 <td>　</td> 
 </tr> 
 <tr> 
 <td colspan="11"> （6）如果没有编写静态构造函数，而这时类中包含带有初始值设定的静态字段，那么编译器会自动生成默认的静态构造函数。</td> 
 </tr> 
 </tbody> 
</table>

**C\#取系统时间的方法**

string  a =  DateTime.Now.ToString( " yyyy\_MM\_dd HH:mm:ss " );  
             string  b  =  DateTime.Now.ToString( " M/d/yyyy hh:mm:ss tt " );  
             string  c  =  DateTime.Now.ToString( " M.d.yyyy hh-mm-ss-tt " );  
             string  d  =  DateTime.Now.ToString( " M.d.yyyy hh.mm.ss tt " );  
             string  ee  =  DateTime.Now.ToString( " M.d.yyyy.hh.mm.ss.tt " );  
             string  f  =  DateTime.Now.ToString( " yyyy/MM/dd " , System.Globalization.DateTimeFormatInfo.InvariantInfo);  
  
             string  g  =  DateTime.Now.ToString( " yyyy/MM/dd/hh/mm/ss " , System.Globalization.DateTimeFormatInfo.InvariantInfo);

简要谈一下您对微软.NET 构架下remoting和webservice两项技术的理解以及实际中的应用

答：WS主要是可利用HTTP，穿透防火墙。而Remoting可以利用TCP/IP，二进制传送提高效率。

求f=1\*2\*4\*8\*16\*32\*64\*128\*256

方法一：利用位运算：

long  sum  =   1 ; 
 for  ( int  i  =   1 ; i  <   9 ; i \++ ) 
\{ 
    sum  \*=   1   <<  i; 
\}

方法二：利用循环：

int  m  =   1 ,s = 1 ;  
             for  ( int  i  =   0 ; i  <   9 ; i \++ )  
            \{  
                s  =  m  \*   1 ;  
                 for  ( int  j  =   0 ; j  <  i; j \++ )  
                \{  
                    m  =  m  \*   2 ;  
                \}  
            \}

**上个月的最后一天**         
         这是一个计算上个月最后一天的例子。它通过从一个月的最后一天这个例子上减去3毫秒来获得。有一点要记住，在Sql     Server中时间是精确到3毫秒。这就是为什么我需要减去3毫秒来获得我要的日期和时间。        
       
                SELECT  dateadd(ms,-3,DATEADD(mm,DATEDIFF(mm,0,getdate()), 0))

转自[http://www.cnblogs.com/ASPNET2008/archive/2008/05/15/1198715.html][http_www.cnblogs.com_ASPNET2008_archive_2008_05_15_1198715.html]

转载于:https://www.cnblogs.com/LeeYongze/archive/2009/12/14/1623758.html

[None.gif]: /images/20211101/efdc9728f47d4bbabede4b824cd013c8.png
[ExpandedBlockStart.gif]: /images/20211101/19cb7e0ac8b946cf8d529c29ba540f72.png
[ContractedBlock.gif]: /images/20211101/3a8470946f90496cbdde837c6cf44c9d.png
[dot.gif]: /images/20211101/11ae44cb0bc04d9f8f385ebb8232146f.png
[InBlock.gif]: /images/20211101/1a6dc27f8cdc4f1c9fdc4b42ae8d3784.png
[ExpandedSubBlockStart.gif]: https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif
[ContractedSubBlock.gif]: https://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif
[ExpandedSubBlockEnd.gif]: /images/20211101/6f04683915aa4119821e8cf23a77d3e0.png
[ExpandedBlockEnd.gif]: /images/20211101/145683d8d0ee4273b07c7e959b5623e8.png
[http_www.cnblogs.com_ASPNET2008_archive_2008_05_15_1198715.html]: http://www.cnblogs.com/ASPNET2008/archive/2008/05/15/1198715.html