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Sunday, April 27, 2008

Using Vb.Net Function in VBA








How to use a VB.Net DLL/TLB in Excel VBA


Here is an example for using the customized .NET Function in Excel VBA. Unfortunately EXcel VBA doesn't have a Array.Sort function. To overcome the shortcomings, we create our own function here in .Net and use the same in Excel VBA

Here are the steps:


  1. Create a class library project in Visual Studio
  2. Add a COM Class item (DND_SortArray in this example)
  3. In the assembly information edit the title, company and provide a meaningful description. This would be seen in the References dialog in Excel
  4. Add the code shown below:


_
  1. Public Class DotNetDud_SortArray

    #Region "COM GUIDs"

    ' These GUIDs provide the COM identity for this class

    ' and its COM interfaces. If you change them, existing

    ' clients will no longer be able to access the class.

    Public Const ClassId As String = "93534c94-9fc1-4a54-b022-338fa7d454c1"

    Public Const InterfaceId As String = "03787ed3-bc65-41a1-9053-d37f390ff94b"

    Public Const EventsId As String = "34d12c14-8afd-44b7-a987-fc2f909724b6"

    #End Region

    ' A creatable COM class must have a Public Sub New()

    ' with no parameters, otherwise, the class will not be

    ' registered in the COM registry and cannot be created

    ' via CreateObject.

    Public Sub New()

    MyBase.New()

    End Sub

    Public Sub SortArray(ByRef arTemp() As String)

    Array.Sort(arTemp)

    End Sub

    End Class

Compile the Project. You will get a DLL and a TLB.

Now open the Excel VBA Editor and add the TLB file to References.

The following code will now use the SortArray .NET Function created

Sub Use_DotNet_Sort()

Dim Cls1 As DotNetDud_SortArray.DotNetDud_SortArray

Set Cls1 = New DotNetDud_SortArray.DotNetDud_SortArray

Dim arTemp(0 To 2) As String

arTemp(0) = "Bottle"

arTemp(1) = "Apple"

arTemp(2) = "Aaron"

Cls1.SortArray arTemp

Set Cls1 = Nothing

End Sub


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3 comments:

  1. Interesting to see an example of a .Net function called from "plain old" VBA.

    How does the performance of this approach compare to using a bubble sort or quick sort function in VBA? Is there a penalty for leaving th VBA thread to access the .Net assembly?

    ReplyDelete
  2. Ideally it shoudn't be a big a performance penalty as the Vb.NET code is a compiled one and used as another DLL by VBA.

    Though the difference in performance wouldn't be felt for small arrays, using .NET function is quicker for large arrays

    ReplyDelete
  3. My limited understanding is that there are differences between DLLs. A COM (VB6 or C++) DLL should interface with VBA without much performance hit. But don't VB.net DLLs require various shims and interface code to talk to VBA?

    ReplyDelete

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