How to Merge two ArrayList Collections in .NET

If you have two ArrayList collections and you want to merge items available in both collections, you can use AddRange method of ArrayList class

ArrayList list1 = new ArrayList(); 
ArrayList list2 = new ArrayList(); 

list1.Add("HTML"); 
list1.Add("XML"); 

list2.Add("CSS"); 
list2.Add("PHP"); 

list1.AddRange(list2);