C# Class MCQs

Question 11: Which of the following statements are TRUE about constructors in C#.NET?

Answer: A, C

The constructor methods cannot be called explicitly and return value. It gets called automatically when you create an object of the class.

Question 12: Is the constructor called multiple times during the lifetime of an object?

Answer: B

The constructor method only called once when the object is created.

Question 13: You have defined the Employee class, which includes the GetSalary() method. You need to ensure that the GetSalary() method can be used only by the Employee class or a class derived from it. Which access modifier should you use for the GetSalary() method?

Answer: C

The protected members can only be accessed from the class itself or from the derived class.

Question 14: What will be the output of the following program?

public class Program
{
	public static void Main(string[] args)
 	{
		for(int i=0;i<4;i++) 
            Print(i);
    }

    public void Print(object o)
    {
        Console.WriteLine(o);
    }
}

Answer: C

Only static members of the class can be accessed in the static methods. Non-static members cannot be accessed from inside static members. The Main() method is the static method whereas the Print() method is not the static method, so you cannot call the Print() method from the Main() method.

Question 15: Which of the following statements is TRUE?

Answer: C

Question 16: Which of the following statements is TRUE?

Answer: A

Question 17: What will be the output of the following program?

public static void Main(string[] args)
{
	display();
}

static void display(int i =10){
    Console.Write(i);
}

Answer: D.

C# allows us to set the default value of the parameters. If the function gets called without any argument, then it will take the default value.

Question 18: What the following statement does?

Object.ReferenceEqual(obj1, obj2)

Answer: B

The ReferenceEqual() method check whether the two objects points to the same object in the memory or not. Consider the following example:

object x = "Hi";
object y = x;
Object.ReferenceEquals(x, y);

Question 19: What will be the output of the following program?

public static void Main(string[] args)
{
	String str1, str2; 
    str1 = "Hello"; 
    str2 = "Hello";
		
	Console.Write(Object.ReferenceEquals(str1, str2));
}

Answer: A

In the above program, str1 and str2 are two variables that point to the same object in the memory. .NET CLR creates only one string object, "Hello" in the memory and point str1 and str2 to it because the value of both strings is "Hello". It is smart enough to create one object in the memory for multiple variables whose values are the same.

Question 20: What will be the output of the following program? 

public static void Main(string[] args)
{
	string str1 = "Hi";
	string str2 = String.Copy(str1);
		
	Console.Write(Object.ReferenceEquals(str1, str2));
}

Answer: B.

The String.Copy() function returns a new object with the same value and so str1 and str2 point to two different objects in the memory.