How to check if collection is empty

Posted on 2009-07-07
Last Modified: 2012-05-07
This line...

            If mcolVendors(sVendor) Is Nothing Then

causes this error...

Run-time error '5':
Invalid procedure call or argument

The offending line is highlighted in a box of stars(*).

I had hoped that finding no items in the collection would return null but instead throws an error. Does anyone know how to check if an item is in a collection?
'Code in the worksheet class module:


Private Sub CommandButton1_Click()


    Dim wkb1 As Workbook, wkb2 As Workbook

    Dim lRowCounter As Long, lColumnCounter As Long

    Dim sFullName1 As String, sFileName1 As String, sFullName2 As String, sFileName2 As String

    Dim sVendor As String

    Dim dTotalCost As Double, dTotalSales As Double


    'sFullName1 = "\\\DATA1\SHARE\Lognet\Channel Change Process\13. IP&E Planning\Templates\Template ProForma Comp\JBK Examples\Data Collection Fields_v13 Routine.xls"

    sFullName1 = "C:\Documents and Settings\dpark\Desktop\Data Collection Fields_v13 Routine.xls"

    sFileName1 = sGetFileName(sFullName1)


    'sFullName2 = "\\\DATA1\SHARE\Lognet\Channel Change Process\13. IP&E Planning\Templates\Template ProForma Comp\JBK Examples\2009 L&G Fall Equipment_Program Sheet.xls"

    sFullName2 = "C:\Documents and Settings\dpark\Desktop\2009 L&G Fall Equipment_Program Sheet.xls"

    sFileName2 = sGetFileName(sFullName2)


    'Make sure both workbooks open

    If bIsWorkbookOpen(sFileName1) Then

        Set wkb1 = Workbooks(sFileName1)



        Set wkb1 = Workbooks.Open(Filename:=sFullName1)


    End If


    If bIsWorkbookOpen(sFileName2) Then

        Set wkb2 = Workbooks(sFileName2)


        Set wkb2 = Workbooks.Open(Filename:=sFullName2)

    End If


    Dim mcolVendors As New Collection


    lRowCounter = 20

    lColumnCounter = 2


    With wkb2.Worksheets("2009")

        Do Until IsEmpty(.Cells(lRowCounter, "B"))

            sVendor = .Cells(lRowCounter, "B").Value


        **  If mcolVendors(sVendor) Is Nothing Then        ** 


                AddVendor sVendor, lRowCounter

            End If


            mcolVendors(sVendor).TotalCost = .Cells(lRowCounter, "N").Value

            mcolVendors(sVendor).TotalSales = .Cells(lRowCounter, "O").Value


    End With    

End Sub


'Code in the clsVendor class module:


Option Explicit


'Public TotalCost1 As Double

'Public TotalSales1 As Double

'Public PercentMargin As Double


Private dSumCost As Double

Private dSumSales As Double


Property Let Name(sVendor As String)

    Name = sVendor

End Property


'Sum TotalCost values

Property Let TotalCost(dTotalCost As Double)

    TotalCost = TotalCost + dTotalCost

End Property


'Sum TotalSales values

Property Let TotalSales(dTotalSales As Double)

    TotalSales = TotalSales + dTotalSales

End Property


'Return TotalCost

Property Get TotalCost() As Double

    TotalCost = TotalCost

End Property


'Return TotalSales

Property Get TotalSales() As Double

    TotalSales = TotalSales

End Property


Public Function PercentMargin() As Double

    GetPercentMargin = (TotalSales1 - TotalCost1) / TotalSales1

End Function


'Code in the modVendor standard module:


Option Explicit


Public mcolVendors As New Collection


Sub AddVendor(sVendor As String, lRowCounter As Long)

    Dim clsVendor As clsVendor


    With wkb2.Worksheets("2009")

        If mcolVendors(sVendor) Is Nothing Then

            Set clsVendor = New clsVendor

            clsVendor.Name = sVendor

'            clsVendor.TotalCost = .Cells(lRowCounter, "N").Value

'            clsVendor.TotalSales = .Cells(lRowCounter, "O").Value

            mcolVendors.Add clsVendor, clsVendor.Name


            MsgBox sVendor & " class object already exists!"


        End If

    End With

End Sub

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Question by:ltdanp22
LVL 47

Accepted Solution

Wayne Taylor (webtubbs) earned 500 total points
ID: 24798400
Use the error to your advantage....

            Dim v As Variant

            sVendor = .Cells(lRowCounter, "B").Value
            On Error Resume Next
            v = mcolVendors(sVendor)
            If Err <> 0 Then
                AddVendor sVendor, lRowCounter
            End If
            On Error GoTo 0

LVL 85

Expert Comment

by:Mike Tomlinson
ID: 24799107
If you don't want to have to trap the error then use a Dictionary object instead of a Collection:

Then you can use the Exists() method:

To use the Dictionary, add a reference to the "Microsoft Scripting Runtime".

Here is a simple Dictionary example:
Option Explicit

' Click on Project --> References and Check the "Microsoft Scripting Runtime" Entry.

Private dct As New Dictionary

Private Sub Form_Load()

    dct.Add "Item #1", "a"

    dct.Add "Item #2", "b"

    dct.Add "Item #3", "c"

    dct.Add "Item #4", "d"

End Sub

Private Sub Command1_Click()

    Dim key As String

    Dim value As Variant


    key = "Item #3"

    If dct.Exists(key) Then

        value = dct(key)

        MsgBox value, vbInformation, key


        MsgBox key, vbExclamation, "Key Not Found"

    End If


    key = "Item #5"

    If dct.Exists(key) Then

        value = dct(key)

        MsgBox value, vbInformation, key


        MsgBox key, vbExclamation, "Key Not Found"

    End If

End Sub

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