Collection is a data type which holds a group of data. Commonly used collections include ArrayList, Queue, Stack, the generic classes such as List, Dictionary are also collections.
using System.Collections; ArrayList al = new ArrayList(); al.Add("Monday"); al.Add("Tuesday"); al.Add("Wednesday"); foreach (string str in al) { ... }
using System.Collections.Generic; using System.Windows.Forms; List<string> lst = new List<string>(); lst.Add("New York"); lst.Add("Houston"); List<int> lst = new List<int> {4,9,18,3}; MessageBox.Show(lst2.Count.ToString()); //4
using System.Collections.Generic; Dictionary<string, int> d = new Dictionary<string, int> { {"Jacobs",28},{"Mary",26} }; Dictionary<string, int> d2 = new Dictionary<string, int>(); d2.Add("Mary",26); d2.Add("Chris",32); d2["John"] = 23;