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Articles Home » C# » C# Questions & Answers ? Inheritance Implementation

C# Questions & Answers ? Inheritance Implementation

C# Questions & Answers – Inheritance Implementation

This section of our 1000+ C# multiple choice questions focuses on implementation of inheritance in C# Programming Language.

1. What will be the output of the following C# code?

```
 class sample
```
```
 {
```
```
     public  int i;
```
```
     void display() 
```
```
     {
```
```
         Console.WriteLine(i);
```
```
     }
```
```
}    
```
```
class sample1 : sample 
```
```
{
```
```
    public  int j;
```
```
    public void display() 
```
```
    {
```
```
        Console.WriteLine(j);
```
```
    }
```
```
}    
```
```
class Program
```
```
{
```
```
    static void Main(string[] args)
```
```
    {
```
```
        sample1 obj = new sample1();
```
```
        obj.i = 1;
```
```
        obj.j = 2;
```
```
        obj.display();
```
```
        Console.ReadLine();
```
```
    }
```
```
}
```

a) 1
b) 3
c) 2
d) Compile Time error

Answer: c
Explanation: class sample & class sample1 both contain display() method, class sample1 inherits class sample, when display() method is called by object of class sample 1, display() method of class sample 1 is executed rather than that of Class sample.

2. What will be the Correct statement in the following C# code?

```
class sample
```
```
{
```
```
    protected int index;
```
```
    public sample()
```
```
    {
```
```
        index = 0;
```
```
    }
```
```
}
```
```
class sample 1: sample
```
```
{
```
```
    public void add()
```
```
    {
```
```
        index += 1;
```
```
    }
```
```
}
```
```
class Program
```
```
{
```
```
    static void Main(string[] args)
```
```
    {
```
```
        sample 1 z = new sample 1();
```
```
        z . add();
```
```
    }
```
```
}
```

a) Index should be declared as protected if it is to become available in inheritance chain
b) Constructor of sample class does not get inherited in sample 1 class
c) During constructing an object referred to by z, Firstly constructor of sample class will be called followed by constructor of sample 1 class
d) All of the mentioned

Answer: d
Explanation: None.

3. The following C# code is run on single level of inheritance. What will be the Correct statement in the following C# code?

```
 class sample
```
```
 {
```
```
     int i = 10;
```
```
     int j = 20;
```
```
     public void display() 
```
```
     {
```

         Console.WriteLine("base method ");

```
     }
```
```
 }    
```
```
 class sample1 : sample 
```
```
 {
```
```
     public  int s = 30;
```
```
 }    
```
```
 class Program
```
```
 {
```
```
     static void Main(string[] args)
```
```
     {
```
```
         sample1 obj = new sample1();
```

         Console.WriteLine("{0}, {1}, {2}", obj.i,  obj.j,  obj.s);

```
         obj.display();
```
```
         Console.ReadLine();
```
```
     }
```
```
 }
```

10, 20, 30
base method

b) 10, 20, 0
c) compile time error
d) base method

Answer: c
Explanation: ‘i’ and ‘ j’ are inaccessible due to protection level. Declare them as public variable and hence will be accessed in code.

4. What will be size of the object created depicted by C# code snippet?

```
 class baseclass
```
```
 {
```
```
     private int a;
```
```
     protected int b;
```
```
     public int c;
```
```
 }
```
```
 class derived : baseclass
```
```
 {
```
```
     private int x;
```
```
     protected int y;
```
```
     public int z;
```
```
 }
```
```
 class Program
```
```
 {
```
```
     static Void Main(string[] args)
```
```
     {
```
```
         derived a = new derived();
```
```
     }
```
```
 }
```

a) 20 bytes
b) 12 bytes
c) 16 bytes
d) 24 bytes

Answer: d
Explanation: Explained in fundamentals of inheritance.

5. What will be the output of the following C# code?

```
class sample
```
```
{
```
```
    public sample()
```
```
    {
```

        Console.WriteLine("THIS IS BASE CLASS constructor");

```
    }
```
```
 }    
```
```
public class sample1 : sample 
```
```
{
```
```
 
```
```
}    
```
```
class Program
```
```
{
```
```
    static void Main(string[] args)
```
```
    {
```
```
        sample1 obj = new sample1();
```
```
        Console.ReadLine();
```
```
    }
```
```
}
```

a) Code executes successfully prints nothing
b) This is base class constructor
c) Compile time error
d) None of the mentioned

Answer: c
Explanation: Base class accessibility level is much less compared to derived class. Declare it public to get desired output.

6. Select the statement which should be added to the current C# code to get the output as 10 20?

```
class baseclass
```
```
{
```
```
    protected int a = 20;
```
```
}
```
```
class derived : baseclass
```
```
{
```
```
    int a = 10;
```
```
    public void math()
```
```
    {
```
```
         /* add code here */
```
```
    }   
```
```
}
```

a) Console.writeline( a + ” ” + this.a);
b) Console.Writeline( mybase.a + ” ” + a);
c) console.writeline(a + ” ” + base.a);
d) console.writeline(base.a + ” ” + a);

Answer: c
Explanation: None.

7. What will be the Correct statement in the following C# code?

```
 class baseclass
```
```
 {
```
```
     int a;
```
```
     public baseclass(int a1) 
```
```
     {
```
```
         a = a1;
```
```
         console.writeline(" a ");
```
```
     }
```
```
     class derivedclass : baseclass
```
```
     {
```

         public derivedclass (int a1) : base(a1)

```
         {
```
```
             console.writeline(" b ");
```
```
         }
```
```
     }
```
```
     class program
```
```
     {
```

         static void main(string[] args)

```
         {
```

             derivedclass d =  new derivedclass(20);

```
         }
```
```
     }
```
```
 }
```

a) Compile time error
b)

b
a

a
b

d) The program will work correctly if we replace base(a1) with base.baseclass(a1)

Answer: c
Explanation: None.
Output :

         a
         b

8. Which C# statement should be added in function a() of class y to get output “i love csharp”?

```
 class x
```
```
 {
```
```
     public void a()
```
```
     {
```
```
         console.write("bye");
```
```
     }
```
```
 }
```
```
 class y : x
```
```
 {
```
```
     public void a()
```
```
     {
```
```
     /* add statement here */
```

         console.writeline("  i love csharp ");

```
     }
```
```
 }
```
```
 class program
```
```
 {
```
```
     static void main(string[] args)
```
```
     {
```
```
         y obj =  new obj();
```
```
         obj.a();
```
```
     }
```
```
 }
```

a) x.a();
b) a();
c) base.a();
d) x::a();

Answer: c
Explanation: None.

9. Which statements are correct?
a) If a base class consists of a member function fun() and a derived class do not have any function with this name. An object of derived class can access fun()
b) A class D can be derived from class C, which is derived from class B which in turn is derived from class A
c) If a base class and a derived class each include a member function with same name, the member function of the derived class will be called by object of derived class
d) All of the mentioned

Answer: d
Explanation: None.

10. What will be the output of the following C# code?

```
class A 
```
```
{
```
```
    public int i;
```
```
    protected int j;
```
```
}    
```
```
class B : A 
```
```
{
```
```
    public int j;
```
```
    public void display() 
```
```
    {
```
```
        base.j = 3;
```
```
        Console.WriteLine(i + " " + j);
```
```
    }
```
```
}    
```
```
class Program
```
```
{
```
```
    static void Main(string[] args)
```
```
    {
```
```
        B obj = new B();
```
```
        obj.i = 1;
```
```
        obj.j = 2;
```
```
        obj.display();     
```
```
        Console.ReadLine();
```
```
    }
```
```
}
```

a) 2 1
b) 1 0
c) 0 2
d) 1 2

Answer: d
Explanation: Both class A & B have members with same name that is j, member of class B will be called by default if no specifier is used. i contains 1 & j contains 2, printing 1 2.
Output:

1, 2

11. What will be the output of the following C# code?

```
 class A
```
```
 {
```
```
     public int i;
```
```
     private int j;
```
```
 }     
```
```
 class B :A 
```
```
 {
```
```
     void display() 
```
```
     {
```
```
         base.j = base.i + 1;
```

         Console.WriteLine(base.i + "  " + base.j);

```
     }
```
```
}    
```
```
class Program
```
```
{
```
```
    static void Main(string[] args)
```
```
    {
```
```
        B obj = new B();
```
```
        obj.i = 1;
```
```
        obj.j = 2;
```
```
        obj.display();     
```
```
        Console.ReadLine();
```
```
    }
```
```
}
```

a) 1, 3
b) 2, 3
c) 1, 2
d) compile time error

Answer: d
Explanation: Class contains a private member variable j, this cannot be inherited by subclass B and does not have access to it.

12. Which of these keywords is used to refer to member of base class from a sub class?
a) upper
b) base
c) this
d) none of the mentioned

Answer: b
Explanation: Whenever a subclass needs to refer to its immediate super class, it can do so by use of the keyword base.

13. Which of these operators must be used to inherit a class?
a) :
b) &
c) ::
d) extends

Answer: a
Explanation:

             class a
             {

             }
             class b : a
             {
              
             }

14. What will be the output of the following C# code?

```
 using System;
```
```
 public class BaseClass
```
```
 {
```
```
     public BaseClass()
```
```
     {
```

         Console.WriteLine("I am a base class");

```
     }
```
```
 }
```
```
 public class ChildClass : BaseClass
```
```
 {
```
```
     public ChildClass()
```
```
     {
```

         Console.WriteLine ("I am a child class");

```
     }
```
```
 static void Main()
```
```
 {
```
```
     ChildClass CC = new ChildClass();
```
```
 }
```
```
 }
```

I am a base class
I am a child class

I am a child class
I am a base class

c) Compile time error
d) None of the mentioned

Answer: a
Explanation: This is because base classes are automatically instantiated before derived classes. Notice the output, The BaseClass constructor is executed before the ChildClass constructor.
Output: I am a base class
I am a child class

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C# Questions & Answers ? Inheritance Implementation

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