How to add TipAttribute to Model for MVC3 - asp.net-mvc-3

Question

I want to create a new attribute TipAttribute that I can use to display helpful tips to my users.
public class EditPersonModel {
[Display(Name = "Full Name")]
[Tip(Message = "Enter the person's full name.")]
public string Name { get; set; }
}
So from my View I would do
<div class="editor-field">
#Html.InputFor(m => m.Name)
#Html.TipFor(m => m.Name)
</div>
and it would render
<div class="editor-field">
<input id="Name" name="Name" type="text" value="">
<div class="tip">Enter the person's full name.</div>
</div>
I know that I would need to write an Extension method for HtmlHelper, but I have no idea what should go inside!
public static MvcHtmlString TipFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression) {
???
}
I've started looking at the implementation of DisplayAttribute within Mvc3 Source Code, but it's very complex and doesn't look like providing my own custom attribute is very easy/pluggable. Is there a standard MVC3-way to do this?
Thank you!

Answer 1

Assuming your tip attribute was made metadata aware:
public class TipAttribute: Attribute, IMetadataAware
{
public string Message { get; set; }
public void OnMetadataCreated(ModelMetadata metadata)
{
metadata.AdditionalValues["tip"] = Message;
}
}
you could:
public static class HtmlExtensions
{
public static IHtmlString TipFor<TModel, TProperty>(
this HtmlHelper<TModel> htmlHelper,
Expression<Func<TModel, TProperty>> expression
)
{
var metaData = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
var tip = metaData.AdditionalValues["tip"] as string;
var div = new TagBuilder("div");
div.AddCssClass("tip");
div.SetInnerText(tip ?? string.Empty);
return new HtmlString(div.ToString());
}
}