Collections

The collections in many aspects are similar to the VO arrays, but they differ from them as you need to specify the type of the elements (of course, you can type the elements as object leaving this completely open.

The collections are available in the namespaces

• System.Collections
• System.Collections.Generic
• System.Collections.Concurrent
• System.Collections.ObjectModel
• System.Collections.Specialized

There are a lot of different Collection classes, but the most important are:

• System.Collections.Generic.List<T>
• System.Collections.Generic.Dictionary<TKey,TValue>
• System.Collections.SortedList
• System.Collections.ArrayList

If you need some help, which Collection class to use, here is a help:

• MSDN: Selecting a collection class
• MSDN: Commonly used collection types

There are a few very important things you should know about collections:

• They are not arrays, and therefore they are 0-based, so the first member of the collection is element 0, and there is no compiler switch that can change this, because it are the classes itself that are written this was
• You cannot change a collection while you are using it in a foreach loop.
• most collections are using generics, to you need to specify the type(s) of the elements in the declaration of the variable

A few code samples (please look at samples for the single classes System.Collections.Generic.List and System.Collections.Generic.Dictionary) for deeper looks):

using System.Collections.Generic
local oList as List<string>
local nCount as int

oList := List<string>{}
oList:Add( "Hi girls" )
oList:Add( "Hi guys" )
nCount := oList:Count                  
foreach cItem as string in oList
  // do something
next
oList:Remove( "Hi guys" )
oList:RemoveAt( 0 )

local oDictionary as Dictionary<int,string>
local nCount as int

oDictionary := Dictionary<int,string>{}
oDictionary:Add( 1, "Hi girls" )
oDictionary:Add( 2, "Hi guys" )
foreach oItem as KeyValuePair<int,string> in oDictionary
  // do something
next