Introduction
I have used Visual Studio 2012 for debugging purpose. But you can use any version of visul studio as per your availability.
using System; class Program { static void Main() { int[] arr = new int[100]; int i, j, num, count = 0; //Reads size of the array Console.WriteLine("Enter size of the array: "); num = Convert.ToInt32(Console.ReadLine()); //Reads elements in array Console.WriteLine("Enter elements in the array: "); for (i = 0; i < num; i++) { arr[i] = Convert.ToInt32(Console.ReadLine()); } //Find all duplicate elements in array for (i = 0; i < num; i++) { for (j = i + 1; j < num; j++) { // If duplicate element found then increment count by 1 if (arr[i] == arr[j]) { count++; break; } } } Console.WriteLine("\n Total number of duplicate elements found in array:"+count); Console.ReadLine(); } }