The Program in  C# Program to find Sum of Series[1+11+111+ 1111+.. n]terms  is given below:

using System;

namespace SumOfSeries
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello Codeauri Family, enter the number of terms in the series:");
            int n = int.Parse(Console.ReadLine());

            int sum = 0;
            int number = 1;

            for (int i = 0; i < n; i++)
            {
                Console.WriteLine(number);
                sum += number;
                number = number * 10 + 1;
            }

            Console.WriteLine("Okay, the sum of the series is: " + sum);
            Console.ReadLine();
        }
    }
}

Output:

Hello Codeauri Family, enter the number of terms in the series:2
1
11
Okay, the sum of the series is: 12

Pro-Tips💡

Here are the step by step execution of above program:

1. Receive the input from the user for the number of terms in the series. This is done using the int.Parse(Console.ReadLine()) method.
2. Initialize a variable sum to store the sum of the series, and initialize a variable number to store the current term in the series. Both variables are set to 0 and 1 respectively.
3. Use a for loop to iterate through the number of terms in the series. In each iteration, the current term is printed, and then added to the sum. The number variable is then updated by multiplying it by 10 and adding 1 to it.
4. After the loop has completed, the sum of the series is printed.
5. Finally, the program waits for the user to press Enter, using Console.ReadLine(), before terminating.