Difference between anonymous class and IDictionary<string,object> for htmlAttributes in ASP.NET MVC?

Question

For example if you check these two extension methods the only difference is type of htmlAttributes so you can pass your htmlAttributes in two different ways:

public static MvcHtmlString TextBoxFor<TModel, TProperty>(
    this HtmlHelper<TModel> htmlHelper,
    Expression<Func<TModel, TProperty>> expression,
    IDictionary<string, object> htmlAttributes);

public static MvcHtmlString TextBoxFor<TModel, TProperty>(
    this HtmlHelper<TModel> htmlHelper,
    Expression<Func<TModel, TProperty>> expression,
    object htmlAttributes);

And use them in either of these ways:

@Html.TextBoxFor(model => model.TagLine,
    new { @placeholder = "We live to make art." })

@Html.TextBoxFor(model => model.TagLine,
    new Dictionary<string, object> { 
        { "placeholder", "We live to make art." } })

I have checked MVC source code and I know in the background they use same method, but the one which accepts the anonymous object uses HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes) to make the anonymous object a dictionary.

In my point of view, views are cleaner to use anonymous object. What do you think guys? Are there any drawbacks to using an anonymous object?

Gagliardi

Answer 1

There's not too much difference, however using the anonymous object is a cleaner and more readable syntax for the caller, and now considered more standard practice. There might be a slight, negligible performance benefit to using IDictionary if you're a fan of micro-optimisation.

The IDictionary overload option has probably stuck since ASP.NET MVC 1.0 CTP days when C# 3.0 and anonymous objects were still quite new. Eilon Lipton's blog post proposing Using C# 3.0 Anonymous Types as Dictionaries gives some background.

Gough

The dictionary overloads are useful in some cases where you already have a dictionary. – Lumpkin

Answer 2

Chris answers all the thing.

I give 1 more reason why use IDictionary: Prior to MVC 3.0, you could not use anonymous object when you need a HTML5 attribute like "data-something" :D

Cheers

Malmo

You can use this with underscore , like : @Html.TextBoxFor(model => model.TagLine, new { data_as_multiple = "true" }) – Gagliardi

From MVC 3.0 onwards you can use an underscore, e.g. new { data_something = "value" }, which will automatically be converted to a dash data-something="value" – Gough

Answer 3

The IDictionary<string, object> is there for a special reason. If you want to adjust the htmlAttributes parameter in a extended function then this is possible. I have several extensions of the Html.TextBox function. I have for example a function thats called: TextBoxOrDisplayForNoDiaCritics. This function enables a TextBox or displays a disabled textbox. Additional it also removes DiaCritics from the textbox. I do this with a Javascript function. The event onchange fires on the input tag. So in this function I add that onchange event with the javascript function name to the htmlAttributes list. If I use a IDictionary thats easy but when I use an object that will be much harder.

So when you start your project its important to recognize what purpose your Html Helpers have to serve. In my case because I recognize the importance in my project I use IDictionary everywhere in my Project.

Moussaka

This is exactly what I am trying to do. Do you pass in a dictionary object from your views (syntax is not as clean as passing in an anonymous object)? Or, if you pass in an anonymous object, how do you convert it to a dictionary so you can add additional attributes? Of course this is possible with reflection but this seems like a common enough scenario that I think they would have built a helper method in MVC for doing this conversion, but I haven't found it so far – Hilel

this is how I pass, does not look so clean but works: @Html.TextBoxWhenEmptyFor(model => model.UAccount, new Dictionary<string, object> { { ModelConstants.Style, ModelConstants.WidthMinZoekButton } }) another way: @Html.Partial("_LogoHeading", new { Logo = "Applicaties", Link = "Applicaties" }.ToExpando() ) because I want to pass properties and thats something that is otherwise not possible dynamically. – Moussaka