<%@ Page Language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

    Protected Sub listManufacturers_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
        Dim listManufacturers, listModels As DropDownList
        Dim dsModelsByManufacturer As AccessDataSource
        Dim currentRowInEdit As Integer = GridView1.EditIndex
        listManufacturers = CType(sender, DropDownList)
        listModels = CType(GridView1.Rows(currentRowInEdit).FindControl("listModels"), DropDownList)
        dsModelsByManufacturer = CType(GridView1.Rows(currentRowInEdit).FindControl("dsModelsByManufacturer"), AccessDataSource)

        dsModelsByManufacturer.SelectParameters("manufacturerID").DefaultValue = listManufacturers.SelectedValue
        listModels.DataBind()
    End Sub

    Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs)
        If (e.Row.RowState And DataControlRowState.Edit) = DataControlRowState.Edit Then
            Dim dv As System.Data.DataRowView = e.Row.DataItem

            ' Preselect correct value in Manufacturers list
            Dim listManufacturers As DropDownList = e.Row.FindControl("listManufacturers")
            listManufacturers.SelectedValue = dv("ManufacturerID")

            ' Databind list of models in dependent drop-down list, preselect value
            Dim listModels As DropDownList = e.Row.FindControl("listModels")
            Dim dsc As AccessDataSource = e.Row.FindControl("dsModelsByManufacturer")
            dsc.SelectParameters("ManufacturerID").DefaultValue = dv("ManufacturerID")
            listModels.DataBind()
            listModels.SelectedValue = dv("ModelID")
        End If
    End Sub

    Protected Sub GridView1_RowUpdating(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewUpdateEventArgs)
        Dim listManufacturers As DropDownList = CType(GridView1.Rows(e.RowIndex).FindControl("listManufacturers"), DropDownList)
        Dim listModels As DropDownList = CType(GridView1.Rows(e.RowIndex).FindControl("listModels"), DropDownList)
        e.NewValues("ManufacturerID") = listManufacturers.SelectedValue
        e.NewValues("ModelID") = listModels.SelectedValue
    End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Cascading DropDownList Controls in a GridView Control</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <br />
        <h1>Cascading DropDownList Controls in Edit Mode of a GridView Control</h1>
        <p>This page illustrates one way to create cascading (dependent) DropDownList controls
           in edit mode of a GridView control. Blog post about this
           <a href="http://mikepope.com/blog/DisplayBlog.aspx?permalink=1708">here</a>.</p>
        <asp:GridView ID="GridView1"
            runat="server"
            AutoGenerateColumns="False"
            DataKeyNames="ItemID"
            DataSourceID="dsCarsForSale"
            OnRowDataBound="GridView1_RowDataBound"
            OnRowUpdating="GridView1_RowUpdating"
             >

            <Columns>
                <asp:CommandField ShowEditButton="True" />
                <asp:BoundField
                    DataField="ItemID"
                    HeaderText="ItemID"
                    InsertVisible="False"
                    ReadOnly="True"
                    SortExpression="ItemID" />

                <asp:TemplateField HeaderText="Manufacturer" SortExpression="Manufacturer">
                    <ItemTemplate>
                        <asp:Label ID="Label1"
                            runat="server"
                            Text='<%# Bind("Manufacturer") %>'>
                        </asp:Label>

                    </ItemTemplate>

                    <EditItemTemplate>
                        <asp:DropDownList
                            ID="listManufacturers"
                            runat="server"
                            DataSourceID="dsManufacturers"
                            DataTextField="Manufacturer"
                            DataValueField="ManufacturerID"
                            autopostback=true
                            OnSelectedIndexChanged="listManufacturers_SelectedIndexChanged">
                        </asp:DropDownList>
                         <asp:AccessDataSource ID="dsManufacturers"
                             runat="server"
                             DataFile="~/App_Data/Cars.mdb"
                             SelectCommand="SELECT [ManufacturerID], [Manufacturer] FROM [Manufacturers]">
                         </asp:AccessDataSource>
                    </EditItemTemplate>
                </asp:TemplateField>

                <asp:TemplateField HeaderText="Model" SortExpression="ModelName">
                    <ItemTemplate>
                        <asp:Label ID="Label2"
                        runat="server"
                        Text='<%# Bind("ModelName") %>'>
                        </asp:Label>

                    </ItemTemplate>

                    <EditItemTemplate>
                       <asp:DropDownList ID="listModels"
                          runat="server"
                          DataSourceID="dsModelsByManufacturer"
                          DataTextField="ModelName"
                          DataValueField="ModelID" />

                      <asp:AccessDataSource
                         ID="dsModelsByManufacturer"
                         runat="server"
                         DataFile="~/App_Data/Cars.mdb"
                         SelectCommand="SELECT [ModelID], [ModelName] FROM [Models] WHERE ([ManufacturerID] = ?)">
                         <SelectParameters>
                             <asp:Parameter Name="ManufacturerID" />
                         </SelectParameters>
                      </asp:AccessDataSource>

                    </EditItemTemplate>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>

        <asp:AccessDataSource ID="dsCarsForSale"
            runat="server"
            DataFile="~/App_Data/Cars.mdb"
            SelectCommand="SELECT CarsForSale.ItemID, CarsForSale.ManufacturerID,
                     CarsForSale.ModelID, Manufacturers.Manufacturer, Models.ModelName
                 FROM (CarsForSale
                    INNER JOIN Manufacturers ON CarsForSale.ManufacturerID = Manufacturers.ManufacturerID)
                 INNER JOIN Models ON CarsForSale.ModelID = Models.ModelID;"
            UpdateCommand="UPDATE [CarsForSale]
                SET [ManufacturerID] = ?, [ModelID] = ?
                WHERE [ItemID] = ?" >
            <UpdateParameters>
                <asp:Parameter Name="ManufacturerID" Type="Int32" />
                <asp:Parameter Name="ModelID" Type="Int32" />
                <asp:Parameter Name="ItemID" Type="Int32" />
            </UpdateParameters>
        </asp:AccessDataSource>

        </div>
    </form>
</body>
</html>