VB.Net – Excel COM Object not getting released [duplicate]

If you are using .Net V4 or greater, give this a try.
Move all your Button1_Click code into a subroutine and call it from Button1_Click. This will allow the objects that are local to that subroutine to go out of scope and thereby be eligible for garbage collection.

Then call a cleanup method that uses the Marshal.AreComObjectsAvailableForCleanup function to determine how many garbage collection cycles are required to free the COM objects.

Remarks

If there are a lot of references between managed and native code with deep dependency graphs it can take a long time for all the objects to clean up. Each time a GC runs it will free up some number of RCWs, which will in turn release the underlying COM objects. Those COM objects will then release their managed references and make more objects available for cleanup the next time a GC runs, which starts the process over again.

The AreComObjectsAvailableForCleanup method provides a way for the application to determine how many cycles of GC.Collect and GC.WaitForPendingFinalizers need to happen in order to clean everything up.

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    ExcelWork()
    Cleanup()
End Sub

Private Sub ExcelWork()
    Dim objExcel As xl.Application
    Dim wbReport As xl.Workbook = Nothing

    objExcel = CreateObject("Excel.Application")

    Try
        wbReport = objExcel.Workbooks.Open("D:\EL\Nicolas\VS Online\Classe A v2\Launcher-v2.2\Resources\Modules\Zoom.xlsm")
    Catch ex As Exception
        Common.WriteDebugLog("Exception line 44")
    End Try
    If wbReport Is Nothing Then
        MsgBox("Erreur d'ouverture du reporting - Code 745.", vbExclamation)
        Exit Sub
    End If

    With objExcel
        .Visible = False
        .ScreenUpdating = False
        .Calculation = xl.XlCalculation.xlCalculationManual
        .DisplayAlerts = False
    End With

    '' Here I do all my processing which I have removed to make the question more simplified

    With objExcel
        .Calculation = xl.XlCalculation.xlCalculationAutomatic
        .ScreenUpdating = True
        .DisplayAlerts = True
    End With

    ''~~> Close & Clean Up
    wbReport.Close(SaveChanges:=False)
    objExcel.Quit()

    MsgBox("Done")
End Sub

Private Sub Cleanup()
    Do
        GC.Collect()
        GC.WaitForPendingFinalizers()
    Loop While Marshal.AreComObjectsAvailableForCleanup
End Sub