Excel VBA与Windows窗体应用程序流程通信

Question

I have been tasked to deal with an application where an excel spreadsheet needs to retrieve / access values directly from the windows form application running on a client side by side. I have been reading on exposing .NET components to COM and I have been able to compile, register and consume them from excel. However, nothing that I have read so far has allowed me to tap directly into the windows process / form running and access some of the values on the form itself because I always have to "New" the .NET object in VBA and cannot access the current thread. My questions are:

• Is it possible to have direct process to process communication between an excel spreadsheet and a windows form application (no intermediary database or file)?
• Is it possible to compile the output of a .NET windows form application into a .dll? So far, I can only get it to generate an .exe.

Please let me know if this is poorly worded and I can try to explain the problem better.

Thank you for your help.

Answer 1

I think the best way is use Messages between windows. Here is a sample to send from vb6 to vb.net, you can adapt it to vba:

vb6 code:

Private Sub cmdSendData_Click()
Dim sString As String
Dim lHwnd As Long
Dim cds As COPYDATASTRUCT
Dim buf(1 To 255) As Byte

sString = Trim$(txtString)
If sString = "" Then Exit Sub
'
' Get the handle of the target application's visible window.
'
lHwnd = FindWindow(vbNullString, cWINDOW_TITLE)
'
' Copy the string into a byte array,
' converting it to ASCII. Assign lpData
' the address of the byte array.
'
Call CopyMemory(buf(1), ByVal sString, Len(sString))
With cds
    .dwData = 3
    .cbData = Len(sString) + 1
    .lpData = VarPtr(buf(1))
End With
'
' Send the string.
'
Call SendMessage(lHwnd, WM_COPYDATA, Me.hwnd, cds)
End Sub

vb.net code:

Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
    If m.Msg = MainForm.WM_COPYDATA Then
      Dim data As CopyData
      Dim message As String

      ' get the data...
      data = CType(m.GetLParam(GetType(CopyData)), CopyData)
      Dim B(255) As Byte
Marshal.Copy(data.lpData, B, 0, 255)
message = System.Text.Encoding.Default.GetString(B
      ' add the message
      Messages.Items.Add(String.Format("{0}: {1}", DateTime.Now.ToShortTimeString(), message))

      ' let them know we processed the message...
      m.Result = New IntPtr(1)
    Else
      MyBase.WndProc(m)
    End If
  End Sub

  Private Const WM_COPYDATA As Integer = &H4A

  <StructLayout(LayoutKind.Sequential)> _
  Private Structure CopyData
    Public dwData As IntPtr
    Public cbData As Integer
    Public lpData As IntPtr
  End Structure