.net - Best Way to Release Excel Interop com Object

Question

Experts, Please let me know the best way I can do this...

I am working on a VB.Net application that uses the Microsoft.Office.Interop.Excel Object Library to create worksheets within a workbook and Pivot Tables within those worksheets.

My code looks something like this:

Dim ExcelApp As New Microsoft.Office.Interop.Excel.Application
Dim wbk As Microsoft.Office.Interop.Excel.Workbook = Nothing
Dim wksRawData As Microsoft.Office.Interop.Excel.Worksheet = Nothing
Dim wksPvtTbl As Microsoft.Office.Interop.Excel.Worksheet = Nothing
Dim pvtCache As Microsoft.Office.Interop.Excel.PivotCache = Nothing
Dim pvtTables As Microsoft.Office.Interop.Excel.PivotTables = Nothing
Dim pvtTable As Microsoft.Office.Interop.Excel.PivotTable = Nothing
Dim r1 As Microsoft.Office.Interop.Excel.PivotField = Nothing
Dim r2 As Microsoft.Office.Interop.Excel.PivotField = Nothing
Dim df1 As Microsoft.Office.Interop.Excel.PivotField = Nothing

Try

... Create the objects, put in the information

Catch ex As Exception
   MessageBox.Show("There was an error creating the Excel file", "Error Creating File", MessageBoxButtons.OK)
Finally

   ReleaseObject(r1)
   ReleaseObject(r2)
   ReleaseObject(df1)
   ReleaseObject(pvtTable)
   ReleaseObject(pvtTables)
   ReleaseObject(pvtCache)
   ReleaseObject(wksRawData)
   ReleaseObject(wksPvtTbl)
   ReleaseObject(wbk)

   ExcelApp.DisplayAlerts = True
   ExcelApp.Quit()
   ReleaseObject(ExcelApp)

   ExcelApp = Nothing
   wbk = Nothing
   wksRawData = Nothing
   GC.Collect()
End Try

Then I have code that looks as follows for my release objects:

Public Sub ReleaseObject(ByRef Reference As Microsoft.Office.Interop.Excel.Application)
    Dim i As Integer
    If Reference IsNot Nothing Then
        i = System.Runtime.InteropServices.Marshal.ReleaseComObject(Reference)

        While i > 0
            i = System.Runtime.InteropServices.Marshal.ReleaseComObject(Reference)
        End While

        Reference = Nothing
    End If
End Sub

Public Sub ReleaseObject(ByRef Reference As Microsoft.Office.Interop.Excel.Workbook)
    Dim i As Integer
    If Reference IsNot Nothing Then
        i = System.Runtime.InteropServices.Marshal.ReleaseComObject(Reference)

        While i > 0
            i = System.Runtime.InteropServices.Marshal.ReleaseComObject(Reference)
        End While

        Reference = Nothing
    End If
End Sub

... etc

I know there are MANY solutions out there for this kind of problem, but I’m getting lost in all the different ones to know what best fits my current situation… Is this a good way to do this and, if not, what is a more efficient way??

Thanks!!!

Answer 1

Don't search and call release manually. The Interop process could still run loose if the application crashes catastrophically.

I would register the Interop process to the OS via Job Objects.

Here is a solution: https://stackoverflow.com/a/1307180/160146