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Editorial Team
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Asked: 2026-05-11T17:24:43+00:00

I’ve got a f(x) that returns a collection of user controls. .Net lets me

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I’ve got a f(x) that returns a collection of user controls. .Net lets me just treat the f(x) name as the collection. Is there something wrong with doing so?

ex)

Private Function GetCcB() As Collection(Of Reports_ucColumn)
    Dim cc As New Collection(Of Reports_ucColumn)
    cc.Add(Me.ucColumn0)
    cc.Add(Me.ucColumn1)
    cc.Add(Me.ucColumn2)
    Return cc
End Function

Then later on, all use the properties on the objects in the collection, like this:

    For i As Integer = 0 To csB.Count - 1
        If csB(i).Contains("Invalid") Or csB(i).Contains("Duplicate") Then
            GetCcB.Item(i).isValid = False
            GetCcB.Item(i).title = csB(i)
            If csB(i).Contains("Invalid") Then : GetCcB.Item(i).errCode = "005W"
            Else : GetCcB.Item(i).errCode = "005W" 'todo - chg this once we get a duplicate col err code
            End If
        Else
            GetCcB.Item(i).isValid = True
            GetCcB.Item(i).title = csB(i)
            GetCcB.Item(i).errCode = String.Empty
        End If
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1 Answer

  1. Editorial Team

    By calling the method each time that you use the collection, what your code is effectively doing is:

    For i As Integer = 0 To csB.Count - 1
   Dim cc As Collection(Of Reports_ucColumn)
   If csB(i).Contains("Invalid") Or csB(i).Contains("Duplicate") Then
      cc = New Collection(Of Reports_ucColumn)
      cc.Add(Me.ucColumn0)
      cc.Add(Me.ucColumn1)
      cc.Add(Me.ucColumn2)
      cc.Item(i).isValid = False
      cc = New Collection(Of Reports_ucColumn)
      cc.Add(Me.ucColumn0)
      cc.Add(Me.ucColumn1)
      cc.Add(Me.ucColumn2)
      cc.Item(i).title = csB(i)
      If csB(i).Contains("Invalid") Then
         cc = New Collection(Of Reports_ucColumn)
         cc.Add(Me.ucColumn0)
         cc.Add(Me.ucColumn1)
         cc.Add(Me.ucColumn2)
         cc.Item(i).errCode = "005W"
      Else
         cc = New Collection(Of Reports_ucColumn)
         cc.Add(Me.ucColumn0)
         cc.Add(Me.ucColumn1)
         cc.Add(Me.ucColumn2)
         cc.Item(i).errCode = "005W" 'todo - chg this once we get a duplicate col err code
      End If
   Else
      cc = New Collection(Of Reports_ucColumn)
      cc.Add(Me.ucColumn0)
      cc.Add(Me.ucColumn1)
      cc.Add(Me.ucColumn2)
      cc.Item(i).isValid = True
      cc = New Collection(Of Reports_ucColumn)
      cc.Add(Me.ucColumn0)
      cc.Add(Me.ucColumn1)
      cc.Add(Me.ucColumn2)
      cc.Item(i).title = csB(i)
      cc = New Collection(Of Reports_ucColumn)
      cc.Add(Me.ucColumn0)
      cc.Add(Me.ucColumn1)
      cc.Add(Me.ucColumn2)
      cc.Item(i).errCode = String.Empty
   End If
Next

    You would never write code like that, would you?

    You can turn the function into a property with lazy initialisation. Then it’s ok to use it over and over, as the collection is only created once:

    Private _cc As Collection(Of Reports_ucColumn)

Private Property CcB As Collection(Of Reports_ucColumn)
   Get
      If _cc Is Nothing Then
         _cc = New Collection(Of Reports_ucColumn)
         _cc.Add(Me.ucColumn0)
         _cc.Add(Me.ucColumn1)
         _cc.Add(Me.ucColumn2)
      End If
      Return _cc
   End Get
End Property

    (Ideally the property should be public in a class and the _cc variable should be private, encapsulated in the class so that only the property could access it.)

    Semantically this works fine also. A function generally does a bit of work, so you shouldn’t call it over and over if you want to use the result over and over. A property on the other hand usually doesn’t do much work, and if the result needs some processing to be created, the property usually does something like lazy initialisation or pre-initialisation to make sure that the work isn’t done more than neccessary.

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