Save DataGridView to XML File Overwrites Existing

[toecutter]

I am saving textbox text to a DGV and then saving the DGV row to a xml file but i cannot workout how to append instead of overwriting.

    Public Sub WwriteToDataGridView()
        'save data to DGV
        With Ddata.DataGridView2
            'https://stackoverflow.com/questions/19162248/index-was-out-of-range-must-be-non-negative-And-less-than-the-size-of-the-colle
            ' Write to cell (0,0)
            '.ColumnCount = 6
            .Columns(0).Name = "REGO"
            .Rows(0).Cells(0).Value = OEM_Specs.TxReg.Text
            .Columns(1).Name = "WHEELBASE"
            .Rows(0).Cells(1).Value = OEM_Specs.TxtWheelBase.Text
            .Columns(2).Name = "REAR OVERHANG"
            .Rows(0).Cells(2).Value = OEM_Specs.TxtReOverhang.Text
            'gvm diff
            .Columns(3).Name = "GVM DIFF"
            .Rows(0).Cells(3).Value = TxtTBMeffectGVM.Text
            'tbw
            .Columns(4).Name = "TBM"
            .Rows(0).Cells(4).Value = TxtTowBallMassVan.Text
            'gvm gain/loss
            .Columns(5).Name = "GVM GAIN LOSS"
            Dim GVMVanEffect2 As Double = CDbl(TxtTBMeffectGVM.Text)
            Dim GgvmGainLoss As Double = TBM - GVMVanEffect2
            .Rows(0).Cells(5).Value = GgvmGainLoss.ToString
        End With
    End Sub

 Public Sub SsaveDataGridViewToDataSet()
        Dim dt As DataTable = New DataTable("data")
        For i As Integer = 0 To Ddata.DataGridView2.ColumnCount - 1
            dt.Columns.Add(Ddata.DataGridView2.Columns(i).Name, GetType(System.String))
        Next
        Dim myrow As DataRow
        Dim icols As Integer = Ddata.DataGridView2.Columns.Count
        For Each drow As DataGridViewRow In Ddata.DataGridView2.Rows
            myrow = dt.NewRow()
            For i As Integer = 0 To icols - 1
                myrow(i) = drow.Cells(i).Value
            Next
            dt.Rows.Add(myrow)
        Next
        dt.WriteXml(My.Computer.FileSystem.SpecialDirectories.MyDocuments & "\weights\data\data.xml")
    End Sub

[wes4dbt]

I don't think there is an append function. But you could just use ReadXML then add any new rows to the datatable then call WriteXml.

[Shaggy Hiker]

I doubt append was implemented, as it would make little sense. An XML file is just a text file. It happens to hold the schema information for the data, along with the data itself, though. What does appending mean for that? It's just writing text, but that text is XML that may or may not match the schema of what is already there. If it doesn't, then you have a corrupted file. There doesn't appear to be any particularly safe means to implement an append in this case.

For your typical text file, appending is simple. For XML, it isn't simple at all.