Here is one item that went ok on test but caused an unexpected situation in production. The following is a method which checks a collection for the presence of an item:

    ' Return True or False if an image is loaded in memory
    ' expC1 Name
    Public Function IsImageInMemory(ByVal tcName As String) As Boolean
        Dim lcName As String = ""
        Dim lcNameToSearch As String = ""
        Dim llFound As Boolean = False
        Dim loObject As Object

        ' Initialization
        lcNameToSearch = UCase(Trim(tcName))

        ' For each image in the collection
        For Each loObject In oProcess.oApp.oImage

            ' Initialization
            lcName = loObject(1)

            ' If we have found it
            If UCase(lcName) = lcNameToSearch Then
                llFound = True

                ' Initialization
                nWidth = loObject(2)
                nHeight = loObject(3)

                Exit For
            End If

        Next

        Return llFound
    End Function

This is executed hundreds of thousands of times per hour. After several hours in production with this new version, I have found out that the oProcess.oApp.oImage collection is not acting as it should. It returns the message "Object reference not set to an instance of an object." at this level:

at Microsoft.VisualBasic.Collection.GetEnumerator()
at Framework.ProcessWeb.IsImageInMemory(String tcName)

I thought using a collection would be safe enough to check for in memory content for several items. Should I have used an array instead?