Indexers are a new concept for xBase developers. They permit to access the properties of an object like an array. Please see this sample class:

class IndexerTest
protect oValues	as List<string>
 
constructor()
 
oValues := List<string>{}
 
return
 
property self[ nIndex as int ] as string
  get
    if oValues:Count >= nIndex
      return oValues[nIndex-1]
    else
      return ""
    endif
  end get
  set	
    while oValues:Count < nIndex
      oValues:Add( "" )
    end
    oValues[nIndex-1]		:= value
  end set
end property
 
end class

This class can be used like this:

function Start( ) as void
local oTest as IndexerTest
local nI as int
 
oTest := IndexerTest{}
oTest[1] := "Chris"
oTest[2] := "Fabrice"
oTest[3] := "Nikos"
oTest[4]:= "Robert"
 
for nI := 1 upto 5
  Console.WriteLine( i"Element {nI}:" + oTest[nI] )
next
 
return

Please see also this Microsoft article: https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/indexers/

And there is also a forum thread about this: Please see https://www.xsharp.info/forum/public-product/839-indexer-syntax