VB.Net Add Workbook to Running EXCEL Instance - excel

Question

I am working on AutoCAD plugin. Trying to implement function where it first looks for already running EXCEL instances so I just Add new workbook to existing instance instead of always creating new process.
My code fails at the point where it tries to find running process. For some reason it always detects running EXCEL process, I checked it at task manager, it is not there so that's why my plugin crashes at Marchal.GetActiveObject method because it's trying to get that running process...
My functions' code so far:
Private Function GetExcelWorksheet() As Excel.Worksheet
Dim excel As Excel.Application
Dim activeWorksheet As Excel.Worksheet = Nothing
Dim wb As Excel.Workbook = Nothing
Dim ws As Excel.Worksheet = Nothing
Dim ExcelInstances As Process() = Process.GetProcessesByName("EXCEL")
If ExcelInstances.Count() = 0 Then
Exit Function
End If
excel = TryCast(Marshal.GetActiveObject("Excel.Application"), Excel.Application)
If excel Is Nothing Then Exit Function
excel.Visible = True
wb = excel.Workbooks.Add
ws = wb.Worksheets(1)
Return ws
End Function

Answer 1

'Excel.vb
Imports System
Imports System.Runtime.InteropServices
Public Module AnythingYouWantToCallIt
Sub Main
Dim Excel as Object
Dim wb as Object
Dim WS as Object
On Error Resume Next
Excel = GetObject(, "Excel.Application")
If Err.number = 429 then
Msgbox("No Excel running")
err.clear
Excel = CreateObject("Excel.Application")
If err.number = 429 then
MsgBox("Excel Not Installed")
err.clear
Else
MsgBox("New Excel has started")
End If
Else
Msgbox("Existing Excel connected to")
End If
WB = Excel.Workbooks.Add
WS = wb.Worksheets(1)
MsgBox(ws.name)
'If in a function
'Main = WS
End Sub
End Module
This does the BASIC way.
To compile above file paste following lines into a batch file and name above file excel.vb. Put the bat file in same folder as excel.vb and double click batch file.
REM Excel.bat
REM This file compiles Excel.vb to Excel.exe
REM To use
REM Excel
Rem Example
Rem
Rem Excel
"C:\Windows\Microsoft.NET\Framework\v4.0.30319\vbc.exe" /target:winexe /out:"%~dp0\Excel.exe" "%~dp0\Excel.vb"
pause
Does not require Visual Studio

Answer 2

One would only add a Workbook, if a Workbook wasn't already open. Try the following (comments are throughout the code):
Create a new project Windows Forms App (.NET Framework)
Add Reference:
VS 2022:
In VS menu, click Project
Select Add Reference...
Click COM
Check Microsoft Excel xx.x Object Library (ex: Microsoft Excel 16.0 Object Library)
Click OK
Add the following Imports
Imports Excel = Microsoft.Office.Interop.Excel
Imports System.Runtime.InteropServices
GetExcelWorksheet:
Private Function GetExcelWorksheet() As Excel.Worksheet
Dim excel As Excel.Application
Dim activeWorksheet As Excel.Worksheet = Nothing
Dim wb As Excel.Workbook = Nothing
Dim ws As Excel.Worksheet = Nothing
'get existing Excel processes
Dim ExcelInstances As Process() = Process.GetProcessesByName("EXCEL")
For Each instance In ExcelInstances
Debug.WriteLine($"ExcelInstances: ProcessName: {instance.ProcessName} Id: {instance.Id}")
Next
If ExcelInstances.Count() = 0 Then
Debug.WriteLine("No Excel instances found")
Exit Function
End If
Debug.WriteLine("Getting Active Excel instance...")
excel = TryCast(Marshal.GetActiveObject("Excel.Application"), Excel.Application)
If excel Is Nothing Then Exit Function
Debug.WriteLine("Setting Excel visible")
'ensure Excel is visible
excel.Visible = True
'get active workbook
wb = excel.ActiveWorkbook
If wb Is Nothing Then
Debug.WriteLine("Adding Workbook...")
wb = excel.Workbooks.Add()
End If
Debug.WriteLine($"wb.Sheets.Count: {wb.Sheets.Count}")
'set worksheet
ws = DirectCast(wb.Sheets(1), Excel.Worksheet)
'activate worksheet
ws.Activate()
'add new Worksheet
ws = DirectCast(wb.Sheets.Add(After:=wb.Sheets(1)), Excel.Worksheet)
ws.Name = "My Worksheet Name" 'set worksheet name
Debug.WriteLine($"wb.Sheets.Count: {wb.Sheets.Count}")
'set value - for A1 also known as 1,1
ws.Cells(1, 1) = $"{DateTime.Now.ToString("HH:mm:ss.fff")}"
Return ws
End Function
Here are some additional methods that may be useful:
Note: If your application has open resources to Excel, Excel may still be running even after clicking the X(in the upper-right corner) of the Excel window. If one opens Task Manager, Microsoft Excel can be seen under "Background processes". To quit Excel, see the code below.
Public Function IsExcelRunning() As Boolean
'get existing Excel processes
Dim ExcelInstances As Process() = Process.GetProcessesByName("EXCEL")
For Each instance In ExcelInstances
Debug.WriteLine($"ExcelInstances: ProcessName: {instance.ProcessName} Id: {instance.Id}")
Next
If ExcelInstances.Count() = 0 Then
Debug.WriteLine($"IsExcelRunning: False")
Return False
End If
Debug.WriteLine($"IsExcelRunning: True")
Return True
End Function
Public Function IsExcelVisible() As Boolean
Dim excel As Excel.Application
'get existing Excel processes
Dim ExcelInstances As Process() = Process.GetProcessesByName("EXCEL")
For Each instance In ExcelInstances
Debug.WriteLine($"ExcelInstances: ProcessName: {instance.ProcessName} Id: {instance.Id}")
Next
If ExcelInstances.Count() = 0 Then
Debug.WriteLine("No Excel instances found")
Exit Function
End If
Debug.WriteLine("Getting Active Excel instance...")
excel = TryCast(Marshal.GetActiveObject("Excel.Application"), Excel.Application)
If excel Is Nothing Then Return False
Debug.WriteLine($"IsExcelVisible: {excel.Visible}")
Return excel.Visible
End Function
Public Sub QuitExcel()
Dim excel As Excel.Application
Dim wb As Excel.Workbook = Nothing
Dim ws As Excel.Worksheet = Nothing
'get existing Excel processes
Dim ExcelInstances As Process() = Process.GetProcessesByName("EXCEL")
For Each instance In ExcelInstances
Debug.WriteLine($"ExcelInstances: ProcessName: {instance.ProcessName} Id: {instance.Id}")
Next
If ExcelInstances.Count() = 0 Then
Debug.WriteLine("No Excel instances found")
Exit Sub
End If
Debug.WriteLine("Getting Active Excel instance...")
excel = TryCast(Marshal.GetActiveObject("Excel.Application"), Excel.Application)
If excel Is Nothing Then Exit Sub
wb = excel.ActiveWorkbook
If wb IsNot Nothing Then
Debug.WriteLine($"Closing Excel Workbook...")
wb.Close(False)
'release resources
System.Runtime.InteropServices.Marshal.FinalReleaseComObject(wb)
End If
Debug.WriteLine($"Quiting Excel.")
'quit Excel
excel.Quit()
'release resources
System.Runtime.InteropServices.Marshal.FinalReleaseComObject(excel)
GC.Collect() 'force garbage collection
End Sub
Resources
Microsoft.Office.Interop.Excel
How do you list all processes on the command line in Windows?
C# Close Excel Instance opened by another application