Difference between anonymous class and IDictionary

问题:

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?

回答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.

回答2:

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.

回答3:

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