What is the @Html.DisplayFor syntax for?

Question

I understand that in Razor, @Html does a bunch of neat things, like generate HTML for links, inputs, etc.

But I don't get the DisplayFor function...

Why would I write:

@Html.DisplayFor(model => model.Title)

when I could just write:

@Model.Title

Answer 1

Html.DisplayFor() will render the DisplayTemplate that matches the property's type.

If it can't find any, I suppose it invokes .ToString().

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If you don't know about display templates, they're partial views that can be put in a DisplayTemplates folder inside the view folder associated to a controller.

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Example:

If you create a view named String.cshtml inside the DisplayTemplates folder of your views folder (e.g Home, or Shared) with the following code:

@model string

@if (string.IsNullOrEmpty(Model)) {
   <strong>Null string</strong>
}
else {
   @Model
}

Then @Html.DisplayFor(model => model.Title) (assuming that Title is a string) will use the template and display <strong>Null string</strong> if the string is null, or empty.

Answer 2

After looking for an answer for myself for some time, i could find something. in general if we are using it for just one property it appears same even if we do a "View Source" of generated HTML Below is generated HTML for example, when i want to display only Name property for my class

    <td>
    myClassNameProperty
    </td>
   <td>
    myClassNameProperty, This is direct from Item
    </td>

This is the generated HTML from below code

<td>
@Html.DisplayFor(modelItem=>item.Genre.Name)            
</td>

<td>
@item.Genre.Name, This is direct from Item
</td>

At the same time now if i want to display all properties in one statement for my class "Genre" in this case, i can use @Html.DisplayFor() to save on my typing, for least

i can write @Html.DisplayFor(modelItem=>item.Genre) in place of writing a separate statement for each property of Genre as below

@item.Genre.Name
@item.Genre.Id
@item.Genre.Description

and so on depending on number of properties.

Answer 3

I think the main benefit would be when you define your own Display Templates, or use Data annotations.

So for example if your title was a date, you could define

[DisplayFormat(DataFormatString = "{0:d}")]

and then on every page it would display the value in a consistent manner. Otherwise you may have to customise the display on multiple pages. So it does not help much for plain strings, but it does help for currencies, dates, emails, urls, etc.

For example instead of an email address being a plain string it could show up as a link:

<a href="mailto:@ViewData.Model">@ViewData.TemplateInfo.FormattedModelValue</a>

Answer 4

DisplayFor is also useful for templating. You could write a template for your Model, and do something like this:

@Html.DisplayFor(m => m)

Similar to @Html.EditorFor(m => m). It's useful for the DRY principal so that you don't have to write the same display logic over and over for the same Model.

Take a look at this blog on MVC2 templates. It's still very applicable to MVC3:

http://www.dalsoft.co.uk/blog/index.php/2010/04/26/mvc-2-templates/

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It's also useful if your Model has a Data annotation. For instance, if the property on the model is decorated with the EmailAddress data annotation, DisplayFor will render it as a mailto: link.