I have been attempting to introduce the IEnumerator interface to replace all
the VB6.Collection objects in my migrated VB6 code.  Having previously been
a delphi programmer I am estatic about the .Net platform, however, i am
having some difficulty due to the lack of examples in the MS .NET help.
Something Borland was very good about - eventually...  Anyway, looking at
this site in C# has been a help
http://www.*-*-*.com/
description for an optimized implementation of the IEnumerator interface
which overrides the GetEnumerator Method has me stumped in VB syntax.  I am
including the code below which appears not to work.  Also, assuming i get
this code working I am not sure how to .Add an object to the Enumerator. Any
help or examples or links to working code would be appreciated.

Thanks,

Mark Staelens
CA - VortalLogic

Public Class VLGenProperties

Implements IEnumerable

Private objGenProperty As EnumGenProperty

'Public Function GetEnumerator() As EnumGenProperty

' GetEnumerator = New EnumGenProperty()

'End Function

Public Function GetEnumerator() As Collections.IEnumerator Implements
System.Collections.IEnumerable.GetEnumerator

GetEnumerator = New EnumGenProperty()

End Function

End Class

Public Class EnumGenProperty

Implements IEnumerator

Private Obj As VLGenProperty

Private Cursor As Integer

ReadOnly Property Current() As Object Implements IEnumerator.Current

Get

Current = Obj

End Get

End Property

Public Sub Reset() Implements System.Collections.IEnumerator.Reset

Cursor = -1

End Sub

Public Function MoveNext() As Boolean Implements
System.Collections.IEnumerator.MoveNext

If Cursor > 0 Then cursor = cursor + 1

End Function

Public Function Enumerator() As VLGenProperty

Enumerator = New VLGenProperty()

End Function

End Class

Public Class VLGenProperty

Public Enum enumVariableType

varInteger = 2

varLong = 3

varSingle = 4

varDouble = 5

varCurrency = 6

varDate = 7

varString = 8

varDecimal = 14

End Enum

Private mstrVariableName As String

Private menumVariableType As enumVariableType

Public Property VariableName() As String

Get

Return mstrVariableName

End Get

Set

mstrVariableName = VariableName

End Set

End Property

Public Property VariableType() As enumVariableType

Get

Return menumVariableType

End Get

Set

menumVariableType = VariableType

End Set

End Property

End Class

Here's a "quick and dirty" example of a strongly-typed custom collection
class:

Public Class Employee
        Public FirstName As String
        Public LastName As String
        Public Age As Short

        Public Sub New(ByVal sFirst As String, ByVal sLast As String,
                                ByVal iAge As Short)
                FirstName = sFirst
                LastName = sLast
                Age = iAge
        End Sub

End Class

Public Class WorkForce
        Inherits System.Collections.Bases.TypedCollectionBase

        Public Function Add(ByVal oEmp As Employee) As Integer
                Return MyBase.InnerList.Add(oEmp)
        End Function

        Public Sub Remove(ByVal oEmp As Employee)
                MyBase.InnerList.Remove(oEmp)
        End Sub

        Public Function Item(ByVal iIdx As Integer) As Employee
                Return CType(MyBase.InnerList.Item(iidx), Employee)
        End Function

End Class

--
Patrick Steele

Lead Software Architect

The sample code at CodeGuru (see below) in C# was optimized to not cast the
return object.  Supposedly it is much faster to return the object inside an
implementation of the Enumerator.  I wonder if using the
System.Collections.Bases.TypedCollectionBase Class is optimized for
performance.  If anyone has any comments i would appreciate it, otherwise i
will be using the TypedCollectionBase as posted.

Thank again

Mark Staelens
CA - VortalLogic

If you're implementing a collection of reference-types (real objects), then
I imagine the performance gain will be neglible since casting is not that
expensive.  Patrick's sample is the more practical design in this case, and
still provides type safety.

--
David.

I noticed in both your "Item" and "Add" methods that there does not appear
to be support for either adding an item to a collection using a key nor
retrieving an item from a collection using a key.  Is there no workaround
for this?

Thanks.

--
Mitch Abaza

--
Patrick Steele

Lead Software Architect

--
Patrick Steele

Lead Software Architect