ASP.NET MVC 3列表 <T> 到IEnumerable <SelectListItem>

Question

I'm not currently happy with the way that my DropDownListFor() objects are populated. I'm attempting to find as generic way of populating IEnumerable as possible. This is what I have so far.

Helper:

public static List<SelectListItem> ToSelectList(IDictionary<string,string> dictionaryItems, string selectedValue, string noSelection, bool search = false)
    {
        List<SelectListItem> items = new List<SelectListItem>();

        if (search)
        {
            items.Add(new SelectListItem { Selected = true, Value = "-1", Text = string.Format("-- {0} --", noSelection) });
        }

        foreach (var item in dictionaryItems)
        {
            items.Add(new SelectListItem
            {
                Text = item.Key,
                Value = item.Value,
                Selected = selectedValue == item.Value ? true : false
            });
        }

        return items
            .OrderBy(l => l.Text)
            .ToList();
    }

Controller:

[HttpGet]
    public ActionResult Index()
    {
        var model = new CreateModel();

        var parentOrganisations = _orgs.FindBy(o => o.OwningOrganisationID == Globals.OrganisationID || o.ID == Globals.OrganisationID)
            .OrderBy(o => o.OrganisationName);

        Dictionary<string, string> items = new Dictionary<string, string>();

        foreach (var item in parentOrganisations)
        {
            items.Add(item.OrganisationName, item.ID.ToString());
        }

        model.Organisations = SelectLists.ToSelectList(items, "-1", "-- None -- ", true);

        return View(model);
    }

View:

<div class="control-group">
        <label class="control-label">Parent Organisation</label>
        <div class="controls">
            @Html.DropDownListFor(m => m.ParentOrganisationID, Model.Organisations, new { @class = "input-xlarge"})
            <p class="help-block">Select a parent organisation to create a branch</p>
        </div>
    </div>

There seems to be A LOT of repetitive code in the controller. It takes a generic list, add's the Value and Text to a Dictionary and then uses that as input for a helper which builds up the select list to send as part of the model.

Does anyone have any better ways to achieve this? I hate having bloat in my controller, and when I get several drop downs on a form this is exactly what will happen in this instance.

Thanks,

EDIT - Thanks to Kenneth's helper method, I've now consolidated the whole thing into one call in the controller:

            model.Organisations = _orgs.FindBy(o => o.OwningOrganisationID == Globals.OrganisationID || o.ID == Globals.OrganisationID)
            .OrderBy(o => o.OrganisationName)
            .ToList()
            .ToSelectList(org => org.OrganisationName, org => org.ID.ToString(), "-1", "None", true);

Answer 1

You could provide callbacks that obtain the key and the value and then use those. Apart from that you can create it as an extension method:

Extension method:

public static List<SelectListItem> ToSelectList<T>(this List<T> Items, Func<T, string> getKey, Func<T, string> getValue, string selectedValue, string noSelection, bool search = false)
    {
        List<SelectListItem> items = new List<SelectListItem>();

        if (search)
        {
            items.Add(new SelectListItem { Selected = true, Value = "-1", Text = string.Format("-- {0} --", noSelection) });
        }

        foreach (var item in Items)
        {
            items.Add(new SelectListItem
            {
                Text = getKey(item),
                Value = getValue(item),
                Selected = selectedValue == getValue(item) ? true : false
            });
        }

        return items
            .OrderBy(l => l.Text)
            .ToList();
    }

Usage:

List<Org>() parentOrganisations = // fetch here
model.Organisations = parentOrganisations.ToSelectList(org => org.ID.ToString(), 
                                                       org => org.OrganisationName,
                                                       "-1", 
                                                       "-- None -- ", 
                                                       true);

Note: I typed this in the SO-editor, so you might have some syntax errors (they should be easy to solve though).

Answer 2

You can do in controller only like this: -

List<SelectListItem> dropdownItems = parentOrganisations
    .Select(item => new SelectListItem
    {
        Value = item.ID.ToString(),
        Text = item.OrganisationName,
        Selected = "-1" == item.ID.ToString() ? true : false
    })
    .ToList();