Catch non-existent dll compile errors

**likestheaction** · 01-07-2009, 08:10 PM

I have created a dll in .NET that i use it in excel. End users who use the excel workbook need to register the dll when they first use the workbook. Sometimes, they fail to register the dll and launch the workbook. The workbook has a reference in it to the .dll. As soon as they try to do anything they get a compile error "User-defined type not defined". This is because:

Dim data
Set data = New unit.Units

and the "unit.dll" has not been registered to work with excel.

What i want to do is to catch and interrupt the compile error gracefully and tell the user to go back and re-register the dll before using the workbook. As it stands now they just see compile error - and well you can imagine when they are looking at the vb screen quite confused.

So i thought maybe i would create a type

Type unit
End Type

but you can't have a type without members. And i'm not sure how this would work once someone registers the user-defined type by the same name.

So - any ideas how to solve this problem?

Thanks,

-lta

**shg** · 01-07-2009, 08:12 PM

Can't you just put On Error Resume Next before the New, and test for an error afterward?

Edit: Never mind that, it's a compile error, sorry.

Switch to late binding, and then test for an error:

Dim oData as Object
On Error Resume Next
Set oData = CreateObject("Unit.Units") ' or whatever the object is
If Err <> 0 Then
    '...

Edit2: Please take a few minutes to read the Forum Rules, and then edit your post to wrap your code with Code Tags.

**likestheaction** · 01-09-2009, 05:12 PM

Thanks. I will try the late binding approach. I also tried below, and it works as well. I found it on some other website. Where UNITS_LIBRARY_NAME is a constant for the name of the dll. In the following example no references or object creation is necessary. So a different approach to the solution than my question indicated.

-lta

On Error GoTo UnitsError

Dim ref As Object
Dim fRef As Boolean
  
fRef = False
For Each ref In ThisWorkbook.VBProject.References
    If ref.Name = UNITS_LIBRARY_NAME Then
        fRef = True
    End If
Next
  
If Not fRef Then
    CheckUnits = False 'where CheckUnits is the name of the function
    MsgBox ("The tool could not verify that the units.dll is installed properly. " + vbCrLf + _
             vbCrLf + _
             "Verify that the units.dll installation was completed.  Please refer to the installation documentation.")
    Exit Function
End If

If fRef Then
    CheckUnits = True
    Exit Function
End If

**shg** · 01-09-2009, 05:18 PM

Don't you still get a compile error if you use early binding in the main code?

You can also test for an add-in using GUID, I think, though I've not used it.

**Leith Ross** · 01-10-2009, 08:07 PM

Hello likestheaction,

Here is a routine that will check if the DLL files exists or not. If it does exist, VBA will attempt to register it. If it doesn't exist, the user is alerted. You can change the file name and path to what you are using.

Sub SelfRegister()

  Dim FileName As String
  Dim SysPath As String
  
    FileName = "user32.dll"
    SysPath = Split(Environ("Path"), ";")(1) & "\"
    
      If Dir(SysPath & FileName) <> "" Then
         Shell "regsvr32.exe " & SysPath & FileName
      Else
        MsgBox FileName & " is missing. Please install this file.", vbInformation
        Exit Sub
      End If
    
End Sub

Sincerely,
Leith Ross

Catch non-existent dll compile errors

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