Isolated Storage in ASP.NET

Hi,

I am trying to stroe data in Isolated Storage, but because of "some reason" it's storing only below value in xml file.

<NewDataSet />

Please find the below code,

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        ds = New DataSet()
        dt = New DataTable()

        ' Declare your Columns - for brevity sake I went with the LameO
        ' constructors, but you can (and should) get more specific 
        Dim LastName As DataColumn
        Dim FirstName As DataColumn
        Dim WT As DataColumn
        Dim Desc As DataColumn

        ' Initialize the columns
        LastName = New DataColumn(TextBox2.Text)
        FirstName = New DataColumn(TextBox1.Text)
        WT = New DataColumn("WT")
        Desc = New DataColumn("Desc")

        ' Add them  to your DataTable
        dt.Columns.Add(LastName)
        dt.Columns.Add(FirstName)
        dt.Columns.Add(WT)
        dt.Columns.Add(Desc)

        ' Add the DataTable to your DataSet
        ds.Tables.Add(dt)
        WriteInIS(ds)
    End Sub
    Friend Function WriteInIS(ByVal ds As DataSet) As DataSet

        'Dim isoStore As IsolatedStorageFile
        isoStore = IsolatedStorageFile.GetStore(IsolatedStorageScope.User Or _
            IsolatedStorageScope.Assembly Or IsolatedStorageScope.Domain, Nothing, Nothing)

        'This line will create the directory. If directory already exists it will simply be ignore and no exception would be raised
        isoStore.CreateDirectory(String.Format("{0}\{1}", FOLDER_PATH, SUB_FOLDER_PATH))

        'This block of code will open the file, write the DataSet xml into it and then save.
        Using writer =
            New StreamWriter(
                New IsolatedStorageFileStream(
                    String.Format("{0}\{1}\{2}", FOLDER_PATH, SUB_FOLDER_PATH, FILE_NAME), FileMode.Create, FileAccess.Write, isoStore))

            ds.WriteXml(writer)
            'writer.Close()
        End Using

    End Function

What could be the problem?