How can I bind a IEnumerable sequence to a container with multiple columns?

Question

I believe that I couldn't find a proper title to explain my problem but I think this is the best possible short explanation.

Please let me explain the details.

I want to show a list of my pictures on a page and using a @foreach loop on MVC 3.

Partial View of this list as below:

@model IEnumerable<Picture>
@foreach (var item in Model)
{
    <a href="@item.PicId">
        <img height="35px" style="padding-top:3px" src="ImageHandler.ashx?id=@item.PicId" id="pictureMy" />
    </a>
}

As you may understand I am sending a list to this partialview and it is placing the pictures on a single column.

It is working without any problem but I want to show 3 pictures for each row but couldn't manage.

Any guidance will be very appreciated.

Thanks in advance for your helps.

Answer 1

You could group them by 3:

@model IEnumerable<Picture>
@foreach (var item in Model.Select((value, index) => new { value, index }).GroupBy(x => x.index / 3))
{
    <div>
    @foreach (var picture in item)
    {
        <a href="@picture.value.PicId">
            <img height="35px" style="padding-top:3px" src="ImageHandler.ashx?id=@picture.value.PicId" id="pictureMy" />
        </a>
    }
    </div>
}

But honestly this grouping is not something that should be done in the view. You should define a view model and then have your controller action perform the grouping and return the view model.

So let's start by defining our view models:

public class PictureViewModel
{
    public int PicId { get; set; }
}

public class GroupedPicturesViewModel
{
    public IEnumerable<PictureViewModel> Pictures { get; set; }
}

then the controller action:

public ActionResult Index()
{
    // fetch the pictures from the DAL or something
    IEnumerable<Picture> pictures = ... 

    // Now build the view model
    var model = pictures
        .Select((value, index) => new { value, index })
        .GroupBy(x => x.index / 3)
        .Select(x => new GroupedPicturesViewModel
        {
            Pictures = x.Select(p => new PictureViewModel
            {
                PicId = p.value.PicId
            })
        }
    );
    return View(model);
}

then the corresponding view:

@model IEnumerable<GroupedPicturesViewModel>
@Html.DisplayForModel()

then the corresponding display template for the GroupedPicturesViewModel type (~/Views/Shared/DisplayTemplates/GroupedPicturesViewModel.cshtml):

@model GroupedPicturesViewModel
<div>
    @Html.DisplayFor(x => x.Pictures)
</div>

and finally the display template for the PictureViewModel type (~/Views/Shared/DisplayTemplates/PictureViewModel.cshtml):

@model PictureViewModel
<a href="@Model.PicId">
    <img class="image" src="@Url.Content("~/ImageHandler.ashx?id=" + Model.PicId)" alt="" />
</a>

One final thing that's bugging me is this anchor. Looks ugly. Don't you think? Looks like spaghetti code.

Let's improve it by writing a custom, reusable HTML helper which will render those pictures:

public static class HtmlExtensions
{
    public static IHtmlString Picture(this HtmlHelper<PictureViewModel> htmlHelper)
    {
        var anchor = new TagBuilder("a");
        var picture = htmlHelper.ViewData.Model;
        var id = picture.PicId.ToString();
        var urlHelper = new UrlHelper(htmlHelper.ViewContext.RequestContext);

        // You probably need another property on your view model here as this 
        // id is suspicious about href but since that's what you had in your 
        // original code I don't know what is your intent.
        anchor.Attributes["href"] = id;
        var image = new TagBuilder("img");
        image.Attributes["alt"] = "";
        image.Attributes["src"] = urlHelper.Content(
            "~/ImageHandler.ashx?id=" + urlHelper.Encode(id)
        );
        image.AddCssClass("image");
        anchor.InnerHtml = image.ToString();
        return new HtmlString(anchor.ToString());
    }
}

and then in the display template we will simply have:

@model PictureViewModel
@Html.Picture()

And that's pretty much it. No need to write loops. Everything works by convention.