ASP.NET MVC - Loading dropdownlists based on selected value

Question

Hi all,

I have a view that looks somewhat similar to this

 <% using (Html.BeginForm()) {%>
    <%= Html.DropDownList("Category") %>
    <%= Html.DropDownList("SubCategory") %>
    <input type="submit" value="Print" />
    <%= Html.ActionLink("Cancel", "Index") %>
<% } %>

I was wondering if anyone knew how i could load the subcategory based on the selected Category? In webforms i'd just use the autopostback event to do this, but i'm a bit confused on how to do this using the mvc framework.

Thanks in advance

Answer 1

Place the dropdown list within a PartialView. Then when you post back do a return PartialView("viewName", model). Then in the return of your jQuery simply replace the partial view with the new html that is returned.

So you're view;

<div id="myPartialView">
  <% Html.PartialView("PartialViewName", model); %>
</div>

Then your jQuery does something like

$('#myPartialView').html = retHtml;

Your C#

return PartialView("PartialViewName", model);

Untested but that's the approach i think you want to take.

Answer 2

transform your view like this:

 <% using (Html.BeginForm()) {%>
    <%= Html.DropDownList("Category", Model.SelectList, new {onchange = "actualize(this);"}) %>
    <div id="selectdiv">
    <% Html.RenderPartial("SubCategories"); %>
    </div>
    <input type="submit" value="Print" />
    <%= Html.ActionLink("Cancel", "Index") %>
<% } %>

<script type="text/javascript">

function actualize(obj)
{
     $.ajax({
        url: url,
        async: true,
        type: 'POST',
        data: { id: obj.value },
        dataType: 'text',
        success: function(data) { $("#selectdiv").html(data); },
        error: function() {
            console.log('Erreur');
        }
    });
}

</script>

create a control called SubCategories.aspx and include in it:

<%= Html.DropDownList("SubCategory",Model.SelectList) %>

create a Model class

public class MyModel
{
    public SelectList SelectList {get;set;}
}

create a controller action

public ActionResult SubCategories(int id)
{
     MyModel model = new MyModel();
     model.SelectList = new SelectList(YourRepository.GetSubCategories(id),"Id","Name");
     return View(model);
}