[Solved] Grid Master Detail Cascading Dropdowns

[ovidiaconescu]

I am using a master-detail Telerik MVC Grid on two levels. 


 - The first level contains a drop-down of Customers and some misc data. 
 - The second level contains a drop-down of Cars that are linked to the customer on the first level and some misc data.


I am now using a foreign key column to show the dropdowns of cars and clients. 
How can the second dropdown be filtered by the customer on the first level?


Code:

@(Html.Telerik().Grid<Models.ClientsModel>()
        .Name("Grid")
        .ToolBar(commands => commands.Insert().ButtonType(GridButtonType.ImageAndText))
        .DataKeys(keys => keys.Add(c => c.ClientLineID))
        .Columns(columns =>
        {
            columns.ForeignKey(o => o.ClientID, (System.Collections.IEnumerable)ViewBag.Client, "ClientID", "Name")
                                                   .Width(330)
                                                   .Title("Client");
            columns.Command(commands =>
                {
                    commands.Edit().ButtonType(GridButtonType.ImageAndText);
                    commands.Delete().ButtonType(GridButtonType.ImageAndText);
                }).Width(250);
        })
        .DetailView(car => car.ClientTemplate(

            Html.Telerik().Grid<Delta.Models.CarModel>()
                        .Name("Car_<#= ClientID #>")
                        .DataKeys(keys => keys.Add(c => c.LineID))
                        .ToolBar(commands => commands.Insert().ButtonType(GridButtonType.ImageAndText))
                        .DataBinding(dataBinding =>
                        {
                            dataBinding.Ajax()
                                .Select("_CarLineIndex", "Client", new { id = "<#= ClientID #>" })
                                .Insert("_CarLineCreate", "Client", new { id = "<#= ClientID #>" })
                                .Update("_CarLineUpdate", "Client")
                                .Delete("_CarLineDelete", "Client");
                        })
                        .Columns(columns =>
                                {
                                    columns.ForeignKey(o => o.CarID, (System.Collections.IEnumerable)ViewBag.Cars,
                                    "CarID", "No")
                                                   .Width(500)
                                                   .Title("Car");
                                    columns.Command(commands =>
                                    {
                                        commands.Edit().ButtonType(GridButtonType.ImageAndText);
                                        commands.Delete().ButtonType(GridButtonType.ImageAndText);
                                    }).Width(200);
                                })
                        .Editable(editing => editing => editing.Mode(GridEditMode.InLine))
                        .Scrollable(c => c.Height("auto"))
                        .Resizable(resizing => resizing.Columns(true))
                        .Reorderable(reorder => reorder.Columns(true))
                        .KeyboardNavigation()
                        .Footer(false)
                        .ToHtmlString()
            ))
        .DataBinding(dataBinding =>
        {
            dataBinding.Ajax()
                .Select("_ClientIndex", "Client")
                .Insert("_ClientCreate", "Client")
                .Update("_ClientUpdate", "Client")
                .Delete("_ClientDelete", "Client");
        })
        .Scrollable(c => c.Height("auto"))
        .Editable(editing => editing.Mode(GridEditMode.InLine))
        .Pageable(o => o.PageSize(50))
        .Filterable()
        .KeyboardNavigation()
        .Groupable())

I am thinking that the code might involve some javascript on the `OnDetailViewExpand` event, but I can't figure out what.
Or it might help to build a custom edit model for the cars dropdown, but I can't have it linked to the clientId.

The only solution I have now is to split the grid into separate views and build cascasing comboboxes there.