XL: Limitations of Passing Arrays to Excel Using Automation

Footnotes

A:

The maximum number of elements in the array is approximately 6550. If you exceed this limit, you receive one or both of the following error messages:

The maximum number of elements in the array that you can pass to Excel using the Excel Transpose function is 4095. If you exceed this limit, you receive the following error message:

B:

The maximum number of elements in the array is 4095. If you exceed this limit, you may receive the following error message:

NOTE: When passing a multidimensional array, you may not receive an error message, but the Excel macro will not run when the total number of elements exceeds 4095.

C:

When defining the array parameter in the Excel macro, it must be defined as a Variant variable or you will receive the following error message when you attempt to run the macro using Automation:

For example, suppose the name of your macro in Excel is AcceptArray. Here is an example of how the array must be defined in the Excel macro:

   Public Sub AcceptArray(ByVal myarray As Variant)
      ' You can pass the parameter either ByVal or ByRef.
      ' To determine the number of elements in the array, use
      ' the UBound function.
   End Sub

D:

The maximum number of elements in the array is 5461. If you exceed this limit, you receive one of the following error messages:

- or -

E:

The maximum number of elements in the array is 5461. If you exceed this limit, you receive the following error message:

F:

The maximum number of elements in the array is limited by available memory or the Excel worksheet maximum size (65536 rows X 256 columns). However, the maximum number of elements in the array that you can pass to Excel using the Excel Transpose function is 5461. If you exceed this limit, you receive the following error message:

G:

The maximum number of elements in the array is limited only by available memory. Also, you do not have to define the parameter as a Variant variable in the Excel macro. However, if you want to pass the array ByVal, you must define the parameter as a Variant variable as in the example in footnote C earlier in this article. You will get a run-time error 13, "Type Mismatch" error, if you do not define the variable as a Variant.

H:


When passing an argument ByRef to an out-of-process Automation server, such as Excel, marshalling of the data is done between the Automation controller (or client) and server since they run in separate processes. This means that when an array is passed to Excel using ByRef, a copy of the array is sent to the address space of Excel. After the Excel procedure runs, a copy of the array is passed back to the client. Although this does allow for passing arguments using ByRef to an out-of-process server, it is not very efficient. On the other hand, when using an in-process automation server (a dynamic-link library (DLL)) and you pass an argument ByRef, this is very efficient since no marshalling is done. The server is using the same array in memory as the client. This is possible since the server runs in the same address space as the client.

Because of marshalling with an out-of-process server such as Excel, it is more efficient to pass the array ByVal instead of ByRef. This way, only one copy is passed to Excel and Excel does not have to pass the copy back to the client. To pass an array ByVal to an Excel macro, you must define the parameter in the Excel macro as a Variant variable. See footnote C earlier in this article for an example.

Sample Visual Basic Procedures

The following sample Microsoft Visual Basic for Applications Sub procedures show how to pass arrays to Excel. The first two procedures show how to populate a range of cells on a worksheet by passing an array to a worksheet range. The third procedure shows how to pass an array to an Excel macro.


The following declarations are used with each example:

Option Explicit
Private xlApp As Object
Private xlBook As Object
Private xlSheet As Object
Passing a 1-Dimensional Array to a Worksheet Range:

   Public Sub OneDimension()
      Const size = 5461
      Dim myarray(1 To size) As Integer
      Set xlApp = CreateObject("Excel.Application")
      xlApp.Visible = True
      Set xlBook = xlApp.Workbooks.Add
      Set xlSheet = xlBook.Worksheets("Sheet1")
      xlSheet.Cells(1, 1).Resize(size, 1).Value = _
         xlApp.Application.Transpose(myarray)
   End Sub

Passing a 2-Dimensional Array to a Worksheet Range:

   Public Sub TwoDimension()
      Const size = 2730
      Dim myarray(1 To size, 1 To 2) As Integer
      ' Number of elements = 2730 * 2 = 5460.
      Set xlApp = CreateObject("Excel.Application")
      xlApp.Visible = True
      Set xlBook = xlApp.Workbooks.Add
      Set xlSheet = xlBook.Worksheets("Sheet1")
      xlSheet.Cells(1, 1).Resize(size, 2).Value = myarray
   End Sub

Passing an Array as an Argument to an Excel Macro:

   Public Sub RunExcelMacro()
      Const size = 5461
      Dim myarray(1 To size) As Integer
      Set xlApp = CreateObject("Excel.Application")
      xlApp.Visible = True
      Set xlBook = xlApp.Workbooks.Open("C:\MyBook.xls")
      xlApp.Run "AcceptArray", myarray
   End Sub

The AcceptArray procedure within a module inside C:\MyBook.xls resembles the following:

   Option Explicit

   Public Sub AcceptArray(ByVal myarray As Variant)
      MsgBox "Size of first dimension: " & UBound(myarray, 1)
   End Sub