ASP.NET MVC 3 Display Template problem

Question

First I have a Display Template in Views > Blog > DisplayTemplates:

@model Domain.Model.BlogPost
<div class="blogSummary">
    @Html.ActionLink(Model.Title, "post", new { Id = Model.PostID }, new { @class = "titleLink" })
    <div class="subInfo">
        Posted by @Model.Author on @Model.PostedDate.ToString("D") | @Model.PostComments.Count
        Comment(s)</div>
    <br />
    <div class="summaryText">
        @Html.Markdown(Model.Body.Length > 300 ? Model.Body.Remove(0, 300) + "..." : Model.Body)
        @Html.ActionLink("(view more)", "post", new { Id = Model.PostID })
    </div>
</div>

Then I have a view:

@model IEnumerable<Domain.Model.BlogPost>
@{
    ViewBag.Title = "Index";
}
@Html.DisplayFor(x => x, "BlogPostSummary")

However, I am getting an error on the DisplayFor():

The model item passed into the dictionary is of type 'System.Data.Objects.ObjectSet`1[Domain.Model.BlogPost]', but this dictionary requires a model item of type 'Domain.Model.BlogPost'.

I'm having a bit of trouble understanding what's going on. What is the best way to use the display template?

kim3er · Accepted Answer · 2011-03-16 20:39:41Z

4

The problem is you're trying to pass in a collection of BlogPosts, when a single BlogPost is expected.

Try:

@Html.DisplayFor(x => x[0], "BlogPostSummary")

Or something like:

@foreach (var post in Model)
    @Html.Display(post)

Note: I'm not convinced the second example is using Html.Display correctly. My suspicion is that the code would be better served using a partial instead of a display template.

UIHint

By default, ASP.NET MVC relies on naming conventions to link BlogPost the class to BlogPost.cshtml the display template. If however, you would like to use CustomBlogPost.cshtml as your display template, you can do so by applying the UIHint attribute.

public class DomainModel {
    [UIHint("CustomBlogPost")]
    public BlogPost Post { get; set; }
}

edited Mar 16, 2011 at 20:39

answered Mar 16, 2011 at 19:44

kim3er

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10 Comments

ChevCast Over a year ago

Interesting. In another app I have, I did this @Html.EditorFor(x => x.Guests) and it worked just fine. The model of the view was of type Invite which had a navigation property Guests of type EntityCollection<Guest>. I was not iterating over the collection; it did it automatically :/

kim3er Over a year ago

My feeling is on this one though, that you should be using a partial instead of a display template. Is there any reason why you haven't?

ChevCast Over a year ago

No reason, I was just told in another question somewhere to avoid looping through collections in my views and to use templates. See the accepted answer here: stackoverflow.com/questions/5070399/… That's where he told me to use editors and display templates.

kim3er Over a year ago

I wasn't aware of that functionality, but it doesn't seem to be applicable to display templates.

ChevCast Over a year ago

It is. I just figured it out. It's because of the naming convention. When I renamed my display template to BlogPost.cshmtl it all started working. This just sucks because I don't want that to be the default display template.

|

jessegavin · Accepted Answer · 2011-03-16 19:46:10Z

2

Try this maybe

@Html.DisplayFor(x => x.First(), "BlogPostSummary")

answered Mar 16, 2011 at 19:46

jessegavin

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1 Comment

Alex Over a year ago

Not sure why [UIHint(...)] doesn't work in MVC 5.x but the above worked. Thanks.

Ryan Lundy · Accepted Answer · 2011-03-24 18:33:48Z

2

I've been working on the same problem, and I think I have a better solution for you. You can loop through the collection and still get this to work:

@foreach(var blogPost in Model)
{
    Html.DisplayFor(x => blogPost, "BlogPostSummary")
}

Using a variable on the left side of a lambda expression doesn't necessarily require you to also use it on the right side. DisplayFor expects an Expression<Func<TModel, TValue>>. TModel is the type of your model, such as IEnumerable<BlogPost>, but TValue can be anything you like. So as long as you have a reference to the current item in your collection, as in the foreach above, you can ignore the left side of the lambda expression.

(But you do have to have the TModel. Html.DisplayFor(() => blogPost, "BlogPostSummary") doesn't work.)

answered Mar 24, 2011 at 18:33

Ryan Lundy

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2 Comments

ChevCast Over a year ago

Right I was aware I could loop in this manner (though it seems hackish and probably better suited to partial views). My issue was that I loved how the display template automatically detected that it was being passed a collection of it's model type and did the looping/repeating implicitly. Unfortunately, this only works if you use the proper naming convention for templates. Which means only one template per type, and I needed more than one template per type. Thanks for the answer though!

JoeBrockhaus Over a year ago

I'm actually doing something like this right now, and the above syntax, while it seems like it should work, will not. You will be able to step into your Template, but the generated html will never get rendered. You have to prepend Html.DisplayFor() with @. Typically this would get you the once in a code block you don't need to prepend statements with '@' error, but apparently there are some special rules.. stackoverflow.com/questions/17412113/…

Yngve B-Nilsen · Accepted Answer · 2011-03-16 19:46:55Z

0

Basically it's because doing an @Html.DisplayFor() implicitly tells MVC that the Model to pass on is the Model of the passing View, i.e. IEnumerable<Domain.Model.BlogPost>

What you need to do is enumerate over the Model, and display each of them:

@foreach(var blogPost in Model){

    Html.RenderPartial("BlogPostSummary", blogPost)

}

Make sure the BlogPostSummary is in the correct folder, and you should be good to go!

answered Mar 16, 2011 at 19:46

Yngve B-Nilsen

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Comments

lost_in_a_musical_note · Accepted Answer · 2024-12-12 21:34:51Z

Necro'ing sorry: Just adding an answer since none these use the automatic id that the requester was asking about. The issue is that you're calling the DisplayTemplate helper with a named template. For some unknown reason, ASP .Net and ASP .Net Core disable the automatic name and id handling when a template name is specified. You should rename your displaytemplate to /Views/Shared/DisplayTemplates/BlogPost.cshtml and remove BlogPostSummary from your callsite.

So:

Template /Views/Shared/DisplayTemplates/BlogPost.cshtml

@model Domain.Model.BlogPost
<div class="blogSummary">
    @Html.ActionLink(Model.Title, "post", new { Id = Model.PostID }, new { @class = "titleLink" })
    <div class="subInfo">
        Posted by @Model.Author on @Model.PostedDate.ToString("D") | @Model.PostComments.Count
        Comment(s)</div>
    <br />
    <div class="summaryText">
        @Html.Markdown(Model.Body.Length > 300 ? Model.Body.Remove(0, 300) + "..." : Model.Body)
        @Html.ActionLink("(view more)", "post", new { Id = Model.PostID })
    </div>
</div>

and wherever you're trying to reference it:

@Html.DisplayFor(x => x)

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