The Program in C# Program to find Armstrong number for Given Range is given below:

using System;

namespace ArmstrongNumber
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello Codeauri Family, enter the lower limit here: ");
            int lower = int.Parse(Console.ReadLine());

            Console.WriteLine("Similarly, enter the upper limit: ");
            int upper = int.Parse(Console.ReadLine());

            Console.WriteLine("Okay, the Armstrong numbers in the given range are: ");
            for (int i = lower; i <= upper; i++)
            {
                if (IsArmstrong(i))
                {
                    Console.WriteLine(i);
                }
            }
            Console.ReadLine();
        }

        static int power(int num, int pow)
        {
            int result = 1;
            for (int i = 0; i < pow; i++)
            {
                result = result * num;
            }
            return result;
        }

        static int numberOfDigits(int num)
        {
            int count = 0;
            while (num > 0)
            {
                count++;
                num = num / 10;
            }
            return count;
        }

        static bool IsArmstrong(int num)
        {
            int pow = numberOfDigits(num);
            int originalNum = num;
            int result = 0;
            while (num > 0)
            {
                int remainder = num % 10;
                result = result + power(remainder, pow);
                num = num / 10;
            }

            return result == originalNum;
        }
    }
}

Output:

Hello Codeauri Family, enter the lower limit here:
1

Similarly, enter the upper limit:
1000
Okay, the Armstrong numbers in the given range are:
1
2
3
4
5
6
7
8
9153
370
371
407

Pro-Tips💡

Here are the step by step execution of above program:

1. The first line using System; includes the System namespace in the program. This namespace includes classes like Console that are used in the program.
2. The next line defines a namespace ArmstrongNumber that contains the program logic.
3. The Program class contains the main method, Main, that is the entry point of the program.
4. In the Main method, the program takes two inputs from the user, the lower and upper limits of the range. These inputs are stored in the lower and upper variables.
5. The program then prints all the Armstrong numbers within the given range. It does this by looping through the range from the lower limit to the upper limit, and checking if each number is an Armstrong number using the IsArmstrong method. If a number is an Armstrong number, it is printed to the console.
6. The power method calculates the power of a number and returns the result. It takes two parameters: num and pow.
7. The numberOfDigits method calculates the number of digits in a given number and returns the count.
8. The IsArmstrong method checks if a number is an Armstrong number. It takes one parameter, num. It first calculates the number of digits in the number, then calculates the sum of cubes of each digit in the number. If the sum is equal to the original number, then the number is an Armstrong number and the method returns true. Otherwise, it returns false.
9. The program ends with a call to Console.ReadLine() that waits for the user to press the enter key before closing the console window.