How to check if collection is empty

Posted on 2009-07-07
Medium Priority
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 = "\\msfs05.lowes.com\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 = "\\msfs05.lowes.com\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 48

Accepted Solution

Wayne Taylor (webtubbs) earned 2000 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 86

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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