Why using worksheet.saveas(savefiledialog1.filename) is failing

Yes dear Patrice ,i got "failed to save " error message when i run the code relative to a bound datagridview( dgv obtained by selecting data from a table in database and put them in dataset,...... ). But when the datagridview is not bound , the code is successfully executed

Now i found the solution. the problem was due to data type in my datagridview. there was type nothing value in some rowcells of datagridview
i added this code : If DataGridView1(j, i).Value IsNot Nothing Then ......end if. so the new code which is working below


Private Sub btnExportToExcel_Click(sender As Object, e As EventArgs) Handles btnExportToExcel.Click
DataGridView1.ReadOnly = True
DataGridView1.AllowUserToAddRows = True
Try
btnExportToExcel.Text = "please wait...."
btnExportToExcel.Enabled = False
SaveFileDialog1.Filter = "Excel document (*.xlsx)|*.xlsx"
If SaveFileDialog1.ShowDialog() = System.Windows.Forms.DialogResult.OK Then
Dim xlApp As Excel.Application
Dim xlWorkbook As Microsoft.Office.Interop.Excel.Workbook
Dim xlWorksheet As Microsoft.Office.Interop.Excel.Worksheet
Dim misvalue As Object = System.Reflection.Missing.Value
Dim i As Integer
Dim j As Integer
xlApp = New Microsoft.Office.Interop.Excel.Application
xlWorkbook = xlApp.Workbooks.Add(misvalue)
xlWorksheet = xlWorkbook.Sheets("sheet1")
For k As Integer = 1 To DataGridView1.Columns.Count
xlWorksheet.Cells(1, k).value = DataGridView1.Columns(k - 1).HeaderText

Next

For i = 0 To DataGridView1.RowCount - 2
For j = 0 To DataGridView1.ColumnCount - 1



If DataGridView1(j, i).Value IsNot Nothing Then


xlWorksheet.Cells(i + 2, j + 1).value = DataGridView1(j, i).Value.ToString
End If

Next
Next

xlWorksheet.SaveAs(SaveFileDialog1.FileName)

xlWorkbook.Close()
xlApp.Quit()

releaseobjectb(xlApp)
releaseobjectb(xlWorksheet)
releaseobjectb(xlWorkbook)
MsgBox("successifully saved" & vbCrLf & "File are saved As:" & SaveFileDialog1.FileName, MsgBoxStyle.Information)
btnExportToExcel.Text = " Export to Ms Excel"
btnExportToExcel.Enabled = False
End If
Catch ex As Exception
MessageBox.Show("Failed to save !!!", "Error message", MessageBoxButtons.OK, MessageBoxIcon.Error)
Return
End Try


End Sub

Private Sub releaseobjectb(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