I've a dropdownlist in a dataGrid. When index of the dropdownlist change, the value is written in table "OrderTabel", column "aantal" of my DataSet...

I use the Autopostback-event for the dropdownlist. When i change index, the page postbacks and the value is been written in the paricular column.
But when rebinding, the selectedindex of the dropdown has become 0 again... So i wanna see the selectedIndex the same as i selected before posting back.

I try to do that with:
drop1.SelectedIndex = CType(myDataTable2.Rows("aantal").value, Integer)

But i get all the time the message:

Input string was not in a correct format

SomeBody knows what the problem is and how to solve it?

Public
Sub eventItemDataBound1(ByVal S As Object, ByVal e As DataGridItemEventArgs)

    Dim drop1 As DropDownList = e.Item.FindControl("myDDL")

   Dim  IndexInDataGrid As Integer = e.Item.ItemIndex

If Not IsNothing(drop1) Then 'zeer belangrijk => drop1 moet eerste bestaan!!!

        Dim myDataSet As DataSet
        Dim myDataTable As DataTable
        myDataSet = CType(Session("data"), DataSet)
        myDataTable = myDataSet.Tables("DDLTabel")
        Dim myDataView As DataView
        myDataView = New DataView(myDataTable)
        Dim myDataTable2 = myDataSet.Tables("OrderTabel")


drop1.SelectedIndex = CType(myDataTable2.Rows(indexInDataGrid)("aantal"), Integer)

        drop1.DataSource = myDataView
        drop1.DataMember = "DDLTabel"
        drop1.DataTextField = "aantal"
        drop1.DataValueField = "aantal"
        drop1.DataBind()
    End If
End Sub