>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?

It is a strange code. What is loObject(1)? Shouldn't you use loObject.Name instead and other properties?

Also, in C# you will need to give a type to the loObject in this code. I don't see a type in your code.