Question

For some reason I’m stuck on this. I need to filter results from a View based on a DropDownList in the same view. The basic idea is this: I have a list of providers that belong to various partners, but the provider list contains ALL the providers together (for all partners). I need to be able to display the providers by partner when someone wants to see just that partner (otherwise, the default listing will be ALL providers). My view currently is the “default” (showing all), but for some reason Im sitting here staring at the monitor (for the last 2 hours!) trying to figure out how to filter these results.

Any suggestions where to start/how to do it?!

Answer 1

EDIT: If you want to do this with jQuery and AJAX (which will provide a better user experience because only the subdivisions list will refresh), see this tutorial.

If I understand correctly, you basically want to do a WebForms-style postback.

Let’s say you have a control with countries and country subdivisions (e.g. states, provinces, etc). When the country changes, you want the appropriate subdivisions to display.

So this would be view:

<% using (Html.BeginForm()) { %>
    <%=Html.DropDownList("Address.CountryId", new SelectList(Country.GetAll(), "Id", "Name"), new { onchange = "this.form.submit();" })%>
    <%=Html.DropDownList("Address.CountrySubdivisionId", new SelectList(CountrySubDivision.GetByCountryId(Model.CountryId), "Id", "Name"))%>
    <input type="submit" name="btnSubmit" value="Submit"/>
<%} %>

This is the key to getting the dependent list to filter:

new { onchange = "this.form.submit();" }

And in the controller, you’d have something like this:

    [AcceptVerbs(HttpVerbs.Post)]
    public ViewResult Index(string btnSubmit)
    {
        if (btnSubmit == null)
        {
            // return the view displayed upon GET
        }
        else
        {
            // process the submitted data
        }
    }

In the above code, if the form submission was triggered by changing the value in a dropdown, btnSubmit will be null. Thus, the action you are POSTing to can tell whether or not the user meant to finalize her changes.