北航软院2014级C#期末考试部分考题解答

博主注：本渣渣水平有限，文中若有不对的地方敬请指出，谢谢。

本文中大部分图片来自老师的PPT，感谢邵老师，想要的可以点击右边QQ联系我：）

一、选择

6.Which of the following is wrong?

①Abstract class could contain non abstract method//抽象类可能没有抽象方法

②A class containing abstract method must be a abstract class.//含有抽象方法的类一定是抽象类

③An abstract class cannot be instantiated.//不能实例化

④An abstract class can be sealed class.

解答：基础知识

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7. Which of the following is right use of generic?

①List<int> f = new List<int>()

②List<int> f = new List()

③List f = new List()

④List<int> f = new List<int>

解答：通用类的使用方法

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8.Which of the statements is correct to declare a two-dimensional array in C#?

①int[][] a

②int a[][]

③int[2]a

④int a[2]

解答：创建数组

            //一维
            int[] a = new int[];
            int[] b = new int[] { , ,  };
            int[] c = { , ,  };

            //非矩阵二维数组
            //int wrong1[1][2];//错误

            int[][] aa = new int[][];// array of references to other arrays
            aa[] = new int[] { , ,  };// cannot be initialized directly
            aa[] = new int[] { , ,  };

            //矩阵二维数组
            int[,] aaa = new int[, ];// block matrix
            int[,] bbb = { { , ,  }, { , ,  } };// can be initialized directly
            int[,,] ccc = new int[, , ];

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9.A property’s ______ accessor enable a client to modify the value of the instance variable associated with the property.

①base             ②this               ③get                ④set

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10. Only the methods that are declared as ______ can be overridden in subclass.

①abstract                 ②virtual          ③new              ④override

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15. In .NET Framework class library, all multithread application related classes are in which following namespace?

①System.SysThread

②System.Thread

③System.Threading

④NetException

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17. In C# variables confined by which of the following modifies can only be accessed by the current assembly?

①public            ②protected            ③internal                ④private

解答：

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17.Which of the following is the right output?

using System;
class A
{
    struct Student
    {
        public int age;
        public string name;
        public Student(int age,string name)
        {
            this.age = age;
            this.name = name;
        }
    };

    static void Main(string[] args)
    {
        Student stu1 = new Student(, " Tom");
        Student stu2 = new Student(, " Jerry");
        stu2 = stu1;
        stu1.age = ;
        stu1.name = "Jerry";
        Console.Write(stu2.age);
        Console.Write(stu2.name);

        Console.ReadKey();
    }
}

①18 Tom                 ②18 Jerry                ③30 Jerry                ④30 Tom

解答：结构体实值类型，赋值之后就把<18,Tom>给了stu2，不管你stu1怎么变，与stu2无关。

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18. Which of the following results is the right output?

ArrayList arr = new ArrayList();
        int[] num = { 1, 3, 5 };
        for (int i = 0; i < num.Length; i++)
        {
            　　arr.Add(num[i]);
        }
        arr.Insert(1, 4);
        Console.WriteLine(arr[2]);

①1          ②3          ③4          ④5

解答：了解insert函数的定义就知道啦。

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19.Which of the following description is true about the keyword “ref”?

①”ref” only passes values from caller(调用者)to callee(被调者)

②”ref” only passes values from the callee to caller

③”ref” must be initialized before its method is called.//方法被调用之前,必须初始化

④None of above

解答：VS爸爸最厉害~

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20.Which of the following description about constants is true?

①Declare the constants with the keyword “static”

②The constants must be initialized when declaring.

③Constants can be assigned repeatedly.

④Constants can be declared first and assigned later.

解答：常量的基本知识

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二、判断

1.Only one method can be called using a delegate.

解答：（F）

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2.If no constructor was declared in a class, the compiler generates default constructor which has no parameter.

解答：（T）可能类不是亲生的吧。（PPT115页）

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3.All methods in an abstract class must be declared as abstract methods.

解答：（F）没这个道理！道理在下面（PPT146页）：

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4.If a base class declares an abstract method, a derived class must implement that method.

解答：（F）派生类确实要实现所有抽象方法，但是派生类也可以继续是抽象的呀！，这样就不用管实不实现了。

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5.Sizeof can be applied to reference types.

解答：（F）

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6.One file could have multiple namespaces.

解答：（T）PPT197页

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7.Nested types can be interfaces and delegates.

解答：（T）PPT131页

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8.If a method is marked as Protected, it will be able to access in the derived class.

解答：（T）

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9.Sizeof can be applied to reference types.（重复了啊啊啊）

10.If a base declares an abstract method, a derived class should implement that method.（握草一个should一个must，搞什么鬼！）

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三、填空

1．In C#, the type System.Int32 map to keyword  _____int______

解答：这个还真没仔细看过，万一考个偏的怎么办。

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2．In C#, if you want to change a thread’s state from suspended into running, what method you should call?  Resume

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3．The following class is often called  _____Generic______

       class Buffer<Element> {

              private Element[] data;

              public Buffer( int size ) {…}

             public void Put(Element x) {…}

                public Element Get() {…}

         }

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4．Every interface member must be __implemented___ or ___inherited____ from a base class.

解答：接口的成员要么自己定义要么继承自父类。

接口不能包含常量、字段、操作符、构造函数、析构函数、任何静态成员、方法的实现；

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5．??????

6．Write the output.

static void Main()
{
    String[] cities = {"London","Vienna","Paris","Linz", "Brussels"};
    //using Linq to Objects
    IEnumerable<string> result = from c in cities
    　　　　　　　　　　　　　　　　　where c.StartsWith("L")
    　　　　　　　　　　　　　　　　　orderby c
    select c.ToUpper();

    foreach (string s in result)
        Console.WriteLine(s);
    Console.ReadKey();
}

解答：原题目好像并不能输出什么啊，改了一下题目，他的意思应该是是要输出result内容。结果如下：

LINZ

LONDON

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7． Fill in the blank

using System;

class Program
{
    static void Main()
    {
        Myclass m = new Myclass();
        int[] s = new int[] { , , , ,  };
        int smax, smin;
        m.MaxMin(s, out smax, out smin);

        Console.WriteLine("{0} {1}", smax, smin);
        Console.ReadKey();
    }
}
class Myclass
{
    public void MaxMin(int[] a, out int max, out int min)
    {
        max = min = a[];
        for (int i = ; i < a.Length; i++)
        {
            if (a[i] > max) max = a[i];
            if (a[i] < min) min = a[i];
        }
    }
}

解答：out的用法（默默在MaxMin前面加了一个public）。

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8．Write the output.

delegate void Notifier (string sender);

void SayHello(string sender)
{
    Console.WriteLine("Hello from " + sender);
}
void SayGoodBye(string sender)
{
     Console.WriteLine("Goodbye from " + sender);
}

    Notifier greetings;
    greetings = SayHello;
    greetings += SayGoodBye;
    greetings("John");
    greetings -= SayHello;
    greetings("John");

解答：代理的基本用法。输出结果：

Hello from John

Goodbye from John

Goodbye from John

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9．Write the result of array A.

static void Main()
{
    int[] A = new int[] { , , , ,  };
    Object[] B = new Object[] { , , , ,  };

    Array.Copy(A, B, );

    foreach (int x in A)
        Console.WriteLine(x);

　　foreach (int x in B)
        Console.WriteLine(x);

　　Console.ReadKey();
}

解答：考察Copy的用法。这里面A没有变哦，反倒是B变成了{1,2,8,9,10}

输出结果（数组A内容）：

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10.Please fill in the blanks.

namespace test
{
    public delegate void OnDBOperate();
    public class UserControlBase : System.Windows.Forms.UserControl
    {
        public event OnDBOperate OnNew;
        private void toolbar_ButtonClick(object sender, System.Windows.Forms.ToolBarButtonClickEventArgs e)
        {
            if (e.Button.Equals(BtnNew))
            {
                //Please write code to call OnNew events
                if (OnNew != null)
                    OnNew();
            }
        }
    }
}

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四、简答

1.What is the difference between virtual method and the abstract method?

解答：抽象方法是只有定义、没有实际方法体的函数，它只能在抽象类中出现，并且在子类中必须重写；抽象方法是一种强制派生类覆盖的方法，必须被派生类覆写的方法，否则派生类将不能被实例化。抽象方法是可以看成是没有实现体的虚方法，如果类中包含抽象方法，那么类就必须定义为抽象类，不论是否还包含其它一般方法。

虚方法则有自己的函数体，已经提供了函数实现，而且允许在子类中重写或覆盖。虚方法可以不在派生类中重写。

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2.C# uses different modifiers to confine the data security. There are 5 different modifiers. Please list out each of them and explain their security level.

解答：简单叙述了一下。

public 公有访问。不受任何限制。
private 私有访问。只限于本类成员访问，子类，实例都不能访问。
protected 保护访问。只限于本类和子类访问，实例不能访问。
internal 内部访问。只限于本项目内访问，其他不能访问。
protected internal 内部保护访问。只限于本项目或是子类访问，其他不能访问。

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3.What are the difference between the value type and the reference type.

Value Type	Reference Type

解答：去年原题，看他这意思是要写三个对比QAQ。

值类型直接存储其值，值类型部署在栈上，初始化为0，false，'\0'等。

而引用类型存储对其值的引用，引用类型部署在托管堆上，初始化为null。

具体详解：http://blog.csdn.net/qiaoquan3/article/details/51202926

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4. Write down the differences between Overloading and Overriding?

解答：陈年老题了。

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5.Please give a brief description about the difference and connection between the class and interface.

Class	Interface

解答：前年原题qwq

对了，看到一篇讲了C#各种对比的帖子，分享给你们，可以参考：http://www.jb51.net/article/37971.htm

最后，大家加油呀，祝下午考试顺利~

作者： AlvinZH

出处： http://www.cnblogs.com/AlvinZH/

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