Home » C#.Net » C#.Net find output programs

C#.Net find output programs (const Keyword) | set 1

Find the output of C#.Net programs | const Keyword | Set 1: Enhance the knowledge of C#.Net const Keyword concepts by solving and finding the output of some C#.Net programs.
Submitted by Nidhi, on February 05, 2021

Question 1:

using System;

namespace Demo
{
    class Program
    {
        const int A = 10;
        
        //Entry point of the program
        static void Main(string[] args)
        {
            int C;
            const int B;
            
            B = 20;

            C = A + B;

            Console.WriteLine(C);
        }
    }

}

Output:

ain.cs(13,24): error CS0145: A const field requires a value to be provided

Explanation:

The above program will generate syntax error because constant B must be initialized at the time of declaration. But we assigned 20 after its declaration.

Question 2:

using System;

namespace Demo
{
    class Program
    {
        const int A = 10;
        const int B;

        Program():B(20)
        {
        }
        //Entry point of the program
        static void Main(string[] args)
        {
            int C;
            
            C = A + B;

            Console.WriteLine(C);
        }
    }
}

Output:

main.cs(8,20): error CS0145: A const field requires a value to be provided
main.cs(10,18): error CS1525: Unexpected symbol `B', expecting `base' or `this'

Explanation:

The above program will generate syntax errors because, in the above program, we tried to initialize const data members using the constructor.

Program():B(20)
{}

But we did not use the correct way to initialized const data members. The above constructor definition looks like the member initializer list in C++, but it is not supported in C#.

Question 3:

using System;

namespace Demo
{
    class Program
    {
        const void Fun()
        {
            Console.WriteLine("Fun() called");
        }
        //Entry point of the program
        static void Main(string[] args)
        {
            Program P = new Program();

            P.Fun();
        }
    }
}

Output:

main.cs(7,15): error CS1547: Keyword `void' cannot be used in this context
main.cs(7,23): error CS0145: A const field requires a value to be provided
main.cs(12,15): error CS1525: Unexpected symbol `void', expecting `class', 
`delegate', `enum', `interface', `partial', or `struct'
main.cs(12,32): error CS1514: Unexpected symbol `[', expecting `.' or `{'
main.cs(12,32): error CS1525: Unexpected symbol `]', expecting `class', `delegate', 
`enum', `interface', `partial', or `struct'
main.cs(14,25): error CS1530: Keyword `new' is not allowed on namespace elements
main.cs(14,28): error CS1525: Unexpected symbol `Program', expecting `class', 
`delegate', `enum', `interface', `partial', or `struct'

Explanation:

The above program will generate syntax errors because we cannot define a constant method in C#, here we defined method Fun() with const keyword, which is not correct.

Question 4:

using System;

namespace Demo
{
    class Program
    {
        void Fun()
        {
            Console.WriteLine("Fun() called");
        }
        //Entry point of the program
        static void Main(string[] args)
        {
            const Program P = null;
            Console.WriteLine("Hello World");
        }
    }
}

Output:

Hello World
Press any key to continue . . .

Explanation:

The above program will print "Hello World" on the console screen. In the above program, we defined method fun() inside the Program class, and we created a const reference of Program class initialized with null and then we print "Hello World" on the console screen.

Question 5:

using System;

namespace Demo
{
    class Program
    {
        void Fun()
        {
            Console.WriteLine("Fun() called");
        }
        //Entry point of the program
        static void Main(string[] args)
        {
            const Program P = new Program();

            P.Fun();
        }
    }
}

Output:

main.cs(14,31): error CS0133: The expression being assigned to `P' 
must be a constant or default value

Explanation:

The above program will generate syntax error because a const reference except string can only be initialized with null, but here we created a const reference for Program class, which is not correct.

---