3 Dropdown List cascade using MVC3 & LinqSql

Question

I have 3 dropdownlist i wanna make 3 dropdownlist with cascade. I am using LinqSql for database..

I have 3 tables Product(id,name), Design(id,master_id,name), Model(id,design_id,name) master_id bound to Product(id), design_id bound to Design(id)..

I want to create one dropdown which is gonna show Products and than when i choose a product its gonna make Design dropdown enabled else it will stay disabled.. also here is the tricky part that i couldnt solve and i need great explanation in here creating 3rd dropdown which is gonna be disabled normally till a Design is chosen.

Each of them gonna populate a lower dropdownlist bound to them.Its like; Product gonna enable and populate Design, Design gonna enable and populate Model. I can do it with 2 dropdowns but when it comes to 3 dropdown i stuck really badly im on (brain-freeze)..

I already checked the other questions couldnt find any solution for my self. As i said im using LinqSql i need a solution about 3 cascadingdropdown list for this type of data reach.

thanks already for anything u can do! and if u can explain Model-View-Controller partials and the parameters and why you use them that would be awesome. Iam kinda beginner at this MVC3.

Answer 1

Forget to set my finished work.. People may wanna see how it happens.. Here is my:

View + Jquery

$(function () {
    $("select#Design").attr('disabled', 'true');
    $("select#Model").attr('disabled', 'true');

    $("select#Product").click(function () {
        var prod = $("select#Product option:selected").val();
        if (prod == "" || prod == 0) {
            $("select#Design").attr('disabled', 'true');
            $("select#Model").attr('disabled', 'true');
        } else {
            $.getJSON('@Url.Content("~/Admin/GetDesigns/")', { productId: prod }, function (data) {
                $("select#Design").empty();
                $("select#Model").empty();
                $.each(data, function (i, c) {
                    $('select#Design').append('<option value="' + c.Value + '">' + c.Text + '</option>');
                })
                $("select#Design").removeAttr('disabled');
                $("select#Design option:first").attr('selected', 'selected');

                var des = $("select#Design option:selected").val();
                if (des == "" || des == 0) {
                    $("select#Model").attr('disabled', 'true');
                } else {
                    $.getJSON('@Url.Content("~/Admin/GetModels/")', { designId: des }, function (data) {
                        $("select#Model").empty();
                        $.each(data, function (i, c) {
                            $('select#Model').append('<option value="' + c.Value + '">' + c.Text + '</option>');
                        })
                        $("select#Model").removeAttr('disabled');
                        $("select#Model option:first").attr('selected', 'selected');
                     })
                  }
               })
            }
         })
     })

reason i use Jquery this way to fill all dropdowns and select first elements as default selection! When i choose an element from first dropdown the other two dropdowns starts to fill themselves and select their first element as default selection.. same code can be used for other dropdowns click function just like this:

            $("select#Design").click(function () {
                var des = $("select#Design option:selected").val();
                if (des == "" || des == 0) {
                    $("select#Model").attr('disabled', 'true');
                } else {
                    $.getJSON('@Url.Content("~/Admin/GetModels/")', { designId: des }, function (data) {
                        $("select#Model").empty();
                        $.each(data, function (i, c) {
                            $('select#Model').append('<option value="' + c.Value + '">' + c.Text + '</option>');
                        })
                        $("select#Model").removeAttr('disabled');
                        $("select#Model option:first").attr('selected', 'selected');
                    })
                }
           });

View

@using (Html.BeginForm("Index", "Admin", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
<table>
    <tr>
        <td style="background-color:#e8eef4;" rowspan="3">
        </td>
        <td style="width:190px; background-color:#e8eef4;">
            @Html.DropDownList("Product", (SelectList)ViewData["ProductList"], "Please Select Product", new { style = "width:190px; padding:4px; margin:4px;" })
        </td>
        <td rowspan="3" style="width:400;">
        </td>
        <td style="background-color:#e8eef4;">
        </td>
        <td style="background-color:#e8eef4;" rowspan="3">
        </td>
    </tr>
    <tr>
        <td style="background-color:#e8eef4;">
            <select id="Design" style="width:190px; padding:4px; margin:4px;">
            <option label="Please Select Design" selected="selected"></option>
            </select>
        </td>
        <td style="background-color:#e8eef4;">
        </td>
    </tr>
    <tr>
        <td style="background-color:#e8eef4;">
            <select id="Model" style=" width:190px; padding:4px; margin:4px;">
            <option label="Please Select Model"></option>
            </select>
        </td>
        <td style="background-color:#e8eef4;">
        </td>
    </tr>
</table>
}

Just cause im using linqtosql and im too lazy to make a repository.. This is my CONTROLLER

public class AdminController : Controller
{
    public linqVipDataContext db = new linqVipDataContext();

    //
    // GET: /Admin/
    public ActionResult Index()
    {
        IEnumerable<SelectListItem> ProductItems = db.Products.AsEnumerable().Select(c => new SelectListItem()
        {
            Text = c.name,
            Value = c.id.ToString(),
            Selected = true,
        });
        SelectList prod = new SelectList(ProductItems, "Value", "Text");
        ViewBag.ProductList = prod;
        return View();
    }


    //
    //Fill the Design List..
    public JsonResult GetDesigns(int productId)
    {
        /*var data = dbs.Designs.Where(d => d.master_id == productId).ToList();*/

        IEnumerable<SelectListItem> DesignItems = db.Designs.Where(c => c.master_id == productId).AsEnumerable().Select(c => new SelectListItem()
        {
            Text = c.name,
            Value = c.id.ToString()
        });
        SelectList des = new SelectList(DesignItems, "Value", "Text");
        return Json(des, JsonRequestBehavior.AllowGet);
    }

    //
    //Fill the Model List..
    public JsonResult GetModels(int designId)
    {   
        /*This code down here! Doesnt work and says it's type is unknown*/
        /*var data = dbs.Models.Where(d => d.design_id == designId).ToList();*/

        /*For that reason im using this code*/
        IEnumerable<SelectListItem> ModelItems = db.Models.Where(d => d.design_id == designId).AsEnumerable().Select(c => new SelectListItem()
        {
            Text = c.name,
            Value = c.id.ToString()
        });
        SelectList mods= new SelectList(ModelItems, "Value", "Text");
        return Json(mods, JsonRequestBehavior.AllowGet);
    }

Json requires Value and Text 2 param seperated for creating a selectlist option.. So i must return my value that way..

I posted this cause i found some breakdowns at ur code, ty again for showing me this solution it gave me the idea and allowed me to solve all problems so this is the fully working code.. Ty again. Hope its usefull.

Answer 2

I would approach the problem something like this:

First, in the controller, we'll set up have the following methods:

public JsonResult GetDesignsForProduct(int productId)
{
  // Instantiate our context and do whatever goo we need to select the objects we want
  using (MyDatabaseContext ctx = new MyDatabaseContext())
  {
     return Json(ctx.Designs.Where(d => d.master_id == productId).ToList(), JsonRequestBehavior.AllowGet);
  }
}

public JsonResult GetModelsForDesign(int designId)
{
  // Instantiate our context and do whatever goo we need to select the objects we want
  using (MyDatabaseContext ctx = new MyDatabaseContext())
  {
     return Json(ctx.Models.Where(d => d.design_id == designId).ToList(), JsonRequestBehavior.AllowGet);
  }
}

I've turned on "get" here; if your data contains sensitive information - user names/e-mail addresses, other proprietary or legally protected data, etc. - you can change this to only allow "post", and modify your Javascript accordingly. See Phil Haack's article.

Also, if you expect this data to change frequently, these methods will cache it by default according to your application's cache settings. You can add an OutputCache attribute on the method to alter this behavior.

Then, in the view you'll have some AJAX plumbing, something like this:

function LoadDesigns() {
    // Get the currently-selected value in our Product dropdown
    var prod = $("#Product").val();

    // Call our controller method and process the list of Design objects
    $.getJSON('@Url.Content("~/ControllerName/GetDesignsForProduct")', { productId: prod },
        function (designs) {
            $("#Design").empty();
            $.each(designs, function (i, c) {
                $("#Design").append(
                    $('<option></option>').val(c.id).html(c.name)
                );
            });
    });
}

function LoadModels() {
    // Get the currently-selected value in our Design dropdown
    var des = $("#Design").val();

    // Call our controller method and process the list of Model objects
    $.getJSON('@Url.Content("~/ControllerName/GetModelsForDesign")', { designId: des },
        function (models) {
            $("#Model").empty();
            $.each(models, function (i, c) {
                $("#Model").append(
                    $('<option></option>').val(c.id).html(c.name)
                );
            });
    });
}

Finally, define all three drop-downs as follows:

@Html.DropDownList("Product", productSelectList, new { onchange = "LoadDesigns()" })
@Html.DropDownList("Design", null, new { onchange = "LoadModels()" })
@Html.DropDownList("Model")

Don't forget that the HTML helpers are really just shortcuts to generate the underlying HTML, and in Razor you frequently just go straight to HTML instead of messing with the helpers. So you could just as easily write these as:

<select id="Product" onchange="LoadDesigns()">
  @foreach (var prod in products) {
    <option value="@prod.id">@prod.name</option>
  }
</select>

<select id="Design" onchange="LoadModels()"></select>

<select id="Model"></select>