C# Class MCQs

Question 21: What will be the output of the following program?

public class Program
{
	public static void Main(string[] args)
 	{
		for(int i=0;i<2;i++)
			Printer.Print(i);
	}
}

public static class Printer
{
    static Printer()
    {
        Console.Write("-constructor-.");
    }

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

Answer: A

Static constructor gets executed only once when any of its methods or properties is accessed for the first time.

Question 22: What will be the output of the following program?

public static void Main(string[] args)
{
    test();     
}
	
void test(){
	Console.Write("test()");
}

Answer: B

Only the static function can be called from another static function. The Test() is not a static function, so the above program would give a compile-time error "An object is required for a non-static field, method or property".

Question 23: What will be the output of the following program?

class Program
{
    static void Main()
    {
        Person p = new Person() {
                FirstName = "James",
                LastName = "Bond"
        };

        Console.Write(p.ToString());
    }
}

class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }

    public override string ToString() => $"{FirstName} {LastName}";
}

Answer: D

Here, the ToString() is called Expression-bodied function, which consist of only one statement.

Learn expression-bodied function in C#.

Question 24: What will be the output of the following program?

using static System.String;

class Program
{
    static void Main()
    {
        string str = null;
        Console.Write(IsNullOrEmpty(str));

        Console.ReadKey();
    }

}

Answer: A

Here, using static System.String is included, and so all the static methods of String class can be called without using the class name String.

Learn using static.

Question 25: What does the following code do?

namespace Business
{
    public static class BusinessRules
    {
        public static bool Compare(this string str, string value)
        {
            return str == value;
        }
    }
}

Answer: C

An extension method can be defined by including this with the first parameter, and the method must be static. Extension methods allow you to inject additional methods without modifying, deriving, or recompiling the original class, struct, or interface. Learn C# extension methods.