Export DataGridView to Excel in vb.net 2.0 Windows Form

Private Sub btn_excel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn_excel.Click
       'Export DataGridView to Excel
       Dim xlapp As Excel.Application
       Dim xlworkbook As Excel.Workbook
       Dim xlworksheet As Excel.Worksheet
       Dim misvalue As Object = System.Reflection.Missing.Value
       Dim i As Integer
       Dim j As Integer
       xlapp = New Excel.Application
       xlworkbook = xlapp.Workbooks.Add(misvalue)
       xlworksheet = xlworkbook.Sheets("Sheet1")
       For i = 0 To gv.RowCount - 2
           For j = 0 To gv.ColumnCount - 1
               xlworksheet.Cells(i + 1, j + 1) = _
                   gv(j, i).Value.ToString()
           Next
       Next
       Dim dialog As New SaveFileDialog
       Dim result As DialogResult = dialog.ShowDialog
       Try
           xlworksheet.SaveAs(dialog.FileName)
       Catch exerr As Exception
       End Try

       xlworkbook.Close()
       xlapp.Quit()

       releaseObject(xlapp)
       releaseObject(xlworkbook)
       releaseObject(xlworksheet)

   End Sub
   Private Sub releaseObject(ByVal obj As Object)
       Try
           System.Runtime.InteropServices.Marshal.ReleaseComObject(obj)
           obj = Nothing
       Catch ex As Exception
           obj = Nothing
       Finally
           GC.Collect()
       End Try
   End Sub