Nick Riggs, Web Developer

The typed html helpers that were introduced in ASP.NET MVC 2 are great. If you not using them, you should be. Basically, you pass them an expression tree pointing at a property in your model and it renders the proper html – complete with a nested-delimited id and name attribute. For example, the follow:

<%= Html.TextBoxFor(m => m.Filters.Occurred.From) %>

Renders:

<input type="text" value="" name="Filters.Occurred.From" id="Filters_Occurred_From">

I recently ran into an issue where I needed to output the id that would be generated by using a typed helper. In the HtmlHelper class, I found a GenerateIdFromName method – but I still needed the generated name for that to work. After digging around in the MVC code for a while (open source is awesome), I found the magic and wrapped it all up into two simple yet helpful extension methods for my HtmlHelper:

public static class HtmlExtensions
{
    public static string NameFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression)
    {
        return htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName( ExpressionHelper.GetExpressionText(expression));
    }

    public static string IdFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression)
    {
        return HtmlHelper.GenerateIdFromName(NameFor(htmlHelper, expression));
    }
}

So from our previous example, this view code:

<%= Html.NameFor(m => m.Filters.Occurred.From) %>
<%= Html.IdFor(m => m.Filters.Occurred.From) %>

Renders:

Filters.Occurred.From
Filters_Occurred_From

You might ask: why would you need to do that? In my case I was dynamically creating a lot of html that needed to be wired up to specific JavaScript objects.

Enjoy.