[RESOLVED] Error when trying to reopen excel file after closing

Okay so I'm able to open an embedded excel file in my form, edit it, save and close it but when I open it back up I get the error:

COM object that has been separated from its underlying RCW cannot be used.

From what I understand this is because I closed the process but other than that I have no idea as I'm only a beginner.

Code:

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Imports Microsoft.Office.Interop
Imports Microsoft.Office.Interop.Excel
Imports Microsoft.Office
Imports Microsoft.Office.Core
Imports System.Runtime.InteropServices


Public Class Form1

    Declare Auto Function SetParent Lib "user32.dll" (ByVal hWndChild As IntPtr, ByVal hWndNewParent As IntPtr) As Integer
    Declare Auto Function SendMessage Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
    Private Const WM_SYSCOMMAND As Integer = 274
    Private Const SC_MAXIMIZE As Integer = 61488

    Private Sub releaseObject(ByVal obj As Object)
        Try

            System.Runtime.InteropServices.Marshal.ReleaseComObject(obj)



        Catch ex As Exception

        Finally
            obj = Nothing


        End Try
    End Sub

    Dim APP As New Excel.Application
    Dim worksheet As Excel.Worksheet
    Dim workbook As Excel.Workbook

    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click

        OpenFileDialog1.ShowDialog()
        workbook = APP.Workbooks.Open(OpenFileDialog1.FileName)
   


        SetParent(APP.Hwnd, Panel1.Handle)
        SendMessage(APP.Hwnd, WM_SYSCOMMAND, SC_MAXIMIZE, 0)

    End Sub




    Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
        workbook.Save()
        workbook.Close()
        APP.Quit()


        releaseObject(worksheet)
        releaseObject(workbook)
        releaseObject(APP)
    End Sub

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Any help would be greatly appreciated!

You quit the excel application in Button3_Click (shame on your naming!). Then you attempt to reuse it in Button2_Click. I think if you initialize the object everytime, it may solve your problem.

Code:

---

    Dim APP As Excel.Application
    Dim worksheet As Excel.Worksheet
    Dim workbook As Excel.Workbook

    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        APP = New Excel.Application

        OpenFileDialog1.ShowDialog()
        workbook = APP.Workbooks.Open(OpenFileDialog1.FileName)
   


        SetParent(APP.Hwnd, Panel1.Handle)
        SendMessage(APP.Hwnd, WM_SYSCOMMAND, SC_MAXIMIZE, 0)

    End Sub




    Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
        workbook.Save()
        workbook.Close()
        APP.Quit()


        releaseObject(worksheet)
        releaseObject(workbook)
        releaseObject(APP)
    End Sub

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This worked perfectly, thank you

I even renamed my buttons!