I have a directory of companies, which have 2 properties which are got from multinode tree pickers, Country and Activity. The contents of these are displayed as a list of checkboxes, and I need to be able to filter the directory according to what is checked.

I am having difficulty getting my head around this. Code is as follows - (with lots of things like styling and accordions and pagination stripped out so there might be tags and brackets missing - the page does work as is without filtering)

I have 2 lists which get the parameters coming in and then combine to one list of what needs to be filtered against. I just don't know how to query the items in showItems helper function to only show these companies. ETA - Should I be able to write something like:

   var items = node.Children.Where(x => (x.IsDocumentType(Rnm_StakeholderCompany.ModelTypeAlias)) && x.IsVisible() && (x.GetPropertyValue<IEnumerable<String>>("Country").Contains("1493")));

I'm getting "Exception Details: System.ArgumentNullException: Value cannot be null. "on this line

(using uskinned Source theme if that makes a difference)

  @inherits UmbracoViewPage<USNSourceWeb.App_Code.USNModels.USNBaseViewModel>
@using USNStarterKit.USNHelpers;
@using System.Globalization;

@{
    Layout = "USNMaster.cshtml";
    Rnm_StakeholderDirectory currentPage = (Rnm_StakeholderDirectory)Model.Content;

    // Get filter Terms - 2 filter lists joined together
    string activityName = !String.IsNullOrEmpty(Request.QueryString["a"]) ? Request.QueryString["a"] : "";
    List<string> afilterList = activityName.Split(',').ToList();

    string countryName = !String.IsNullOrEmpty(Request.QueryString["c"]) ? Request.QueryString["c"] : "";
    List<string> cfilterList = countryName.Split(',').ToList();

    afilterList.AddRange(cfilterList);
    foreach(var str in afilterList)
    {
        <p>@str</p>
    }


    Umbraco.TypedMedia().Where(Property("Country")(afilterList));
    IPublishedContent activityList = Umbraco.TypedMedia(Rnm_StakeholderCompany.GetModelPropertyType<string>("Activity"));




    int pageSize = int.TryParse(currentPage.GetProperty("pageSize").Value.ToString(), out pageSize) ? pageSize : 15;
    int page = int.TryParse(Request.QueryString["page"], out page) ? page : 1;


    IEnumerable<IPublishedContent> posts = currentPage.Children.Where(x => (x.IsDocumentType(Rnm_StakeholderCompany.ModelTypeAlias)) && x.IsVisible());
    //if (activityName != null)
    //{
    //posts = currentPage.Children.Where(x => (x.GetPropertyValue<string>("Activity").Split(",".ToCharArray()).Contains("Trade")) && x.IsVisible());

    //}

    @*foreach (var onepage in posts)
    {
        <span>@onepage.GetPropertyValue("Activity").ToString().Split(",".ToCharArray())</span>
    }*@

int postCount = posts.Count();
var totalPages = (int)Math.Ceiling((double)postCount / (double)pageSize);

IPublishedContent parent = currentPage.AncestorOrSelf(1);
IEnumerable<IPublishedContent> activitylist = parent.Children().Where(x => (x.IsDocumentType(ActivityList.ModelTypeAlias)) && x.IsVisible());
IPublishedContent activities = activitylist.First();

IEnumerable<IPublishedContent> countrylist = parent.Children().Where(x => (x.IsDocumentType(CountryList.ModelTypeAlias)) && x.IsVisible());
IPublishedContent countries = countrylist.First();

}

            @Html.Partial("USNMiscPageElements/USN_StandardPageHeaderSection", Model)


<!-- CONTENT -->
<section class="content">
        @{


            if (posts.Count() > 0)
            {
                <div class="container">


                            <form method="get" action="@Request.Url.ToString()">

                                <p>
                                    FILTER LIST BY: ACTIVITY/INTEREST 
                                                <ul class="directory-filter">
                                                    @foreach (IPublishedContent item in activities.Children().OrderBy("SortOrder"))
                                                    {
                                                        string selected = "";
                                                        foreach (string str in afilterList)
                                                        {
                                                            if (item.Name == str)
                                                            {
                                                                selected = "checked";
                                                            }
                                                        }
                                                        <li><input type="checkbox" name="a" value="@item.Id" @selected />@item.Name</li>
                                                    }
                                                </ul>

                                                    COUNTRY 
                                                <ul class="directory-filter">
                                                    @foreach (IPublishedContent item in countries.Children().OrderBy("SortOrder"))
                                                    {
                                                        string selected = "";
                                                        foreach (string str in afilterList)
                                                        {
                                                            if (item.Name == str)
                                                            {
                                                                selected = "checked";
                                                            }
                                                        }
                                                        <li><input type="checkbox" name="c" value="@item.Id" @selected />@item.Name</li>
                                                    }
                                                </ul>


                     <button type="submit" class="btn btn-sm c1-bg c6-text">Submit</button>
                    </form>
                </div>
        <div class="directory-grid col-md-9 col-xs-12">
                @showItems(@currentPage, (pageSize), page)    
        </div>





            // pagination

        }


    }
    <!--// CONTAINER standard -->

</section>

<!--// CONTENT -->
<!-------   EACH INDIVIDUAL ITEM  ------->

@helper showItems(IPublishedContent node, int count, int page)
{
var items = node.Children.Where(x => (x.IsDocumentType(Rnm_StakeholderCompany.ModelTypeAlias)) && x.IsVisible()).Skip((page - 1) * count).Take(count);

//var items = node.Children.Where(x => (x.IsDocumentType(Rnm_StakeholderCompany.ModelTypeAlias)) && x.IsVisible() && (x.GetPropertyValue<IEnumerable<IPublishedContent>>("Country").ToString() == "Austria")).Skip((page - 1) * count).Take(count);


//var careersList = Umbraco.TypedContentAtRoot().DescendantsOrSelf("CareersList").FirstOrDefault();
//var careerItems = careersList.Children.Where("Visible");

//var items = node.Children.Where(x => (x.GetPropertyValue<string>("Country")=="Austria"));

foreach (var item in items)
{
    string itemTitle = item.HasValue("onPageTitle") ? itemTitle = item.GetProperty("onPageTitle").Value.ToString() : item.Name;


        <div class="row directory-company">                
            <div class="col-xs-10">
                <p><a href="@item.Url">@itemTitle</a></p>
            </div>

        </div>

    var people = item.Children.Where(x => (x.IsDocumentType(PersonListing.ModelTypeAlias)) && x.IsVisible());
    foreach (var person in people)
    {
        string personTitle = person.HasValue("onPageTitle") ? personTitle = person.GetProperty("onPageTitle").Value.ToString() : person.Name;
            <div class="row directory-person">
                <div class="col-md-5 col-xs-12 col-md-offset-1">
                    <p><a href="@person.Url">@personTitle</a></p>
                </div>

            </div>
        }
}

}