The basic difference between an Array and ArrayList are :

Arrays are of fixed size, where as ArrayList can grow dynamically in size. Array occupies memory in Stack where as ArrayList occupies Heap. Also, ArrayList are not type-safe, single arraylist can contain different datatypes.

Let us go by a sample:

Step 1: Create a console application.

Step 2: Create a ArrList class as shown below.

 

public class ArrList     {         public string msg = "String of ArrList Class";         string[] sl = new string[3];        // Array is of fixed size, Type Safe         ArrayList al = new ArrayList();     // Array List size is dynamic , Not Type Safe         public void AddItem()         {             //Permissible members are string only             sl[0] = "Hi";             sl[1] = "Hello";             sl[2] = "Welcome";             //Permissible members are of any data type             al.Add("String Msg");   //Adding String             al.Add(1);              //Adding Integer             al.Add('c');            //Adding Char             ArrList ob = new ArrList();             al.Add(ob);             //Adding userdefined class instance         }         public void ReadItem()         {             int i;             Console.WriteLine("Printing Array");             for (i = 0; i < 3; i++)             {                 Console.Write(sl[i]+"//");             }             i = 0;             Console.WriteLine("\n"+"Printing ArrayList");             foreach (var itm in al)             {                 Console.Write(itm + "//");             }         }     }

Step 3: In main method, use the below code

Console.WriteLine("//**********Array and ArrayList******************");

            ArrList myAr = new ArrList();

            myAr.AddItem();

            myAr.ReadItem();

I hope this article will help to understand the difference.