Explain what is different and how it works

Please, revise this code example C# for Finding the duplicates and follow the discussion question below. Apart from code, the writing part is just 150 words
//function to display the duplicate values in an Array
public void DisplayArray(ArrayList ary)
//loop through all the elements
for (int i = 0; i < ary.Count; i++)
Console.Write(ary[i]+” “);
//function to find the duplicate values in an Array
public void FindDuplicate(ArrayList ary)
//Array list to store all the duplicate values
ArrayList dup = new ArrayList();
for (int i = 0; i < ary.Count;i++)
for (int j =i+1; j < ary.Count; j++)
//compare each value with following remaining values
if (ary[i].Equals(ary[j]))
//When duplicate value is found, check
//whether the value not contained in the dup array list
//if not contains, then add the value to dup array list
Console.WriteLine(“The numbers which duplicates are”);
//Input Arraylist values: 4,5,2,5,4,7
Output: 4 5 2 5 4 7
The numbers which are duplicates:
After reading week 2 required materials and conducting independent research as needed, discuss with your peers the following:
The solution uses an ArrayList object. Modify it and make it run with code that uses a different approach to solve the problem with identical results:
post an alternative solution(it must run on Visual Studio)
explain what is different and how it works
compare the ArrayList approach with the alternative solution, evaluate which one is more effective, and explain why.