How to read property data annotation value in .NET MVC

Question

I Just starting out w/ ASP.NET MVC 3 and I am trying to render out the following HTML for the string properties on a ViewModel on the create/edit view.

Answer 1

To do this you'll need to create your own HtmlHelper extension and use reflection to get at the attributes on the model property. Look at the source code at http://codeplex.com/aspnet for the existing ...For() HtmlHelper extensions. You'll need to get the PropertyInfo object for the model property using the expression that is passed in as the argument. They have several helper classes that should serve as templates for this. Once you have that, use the GetCustomAttributes method on the PropertyInfo to find the StringLength attribute and extract it's value. Since you'll be using a TagBuilder to create the input, add the length as an attribute via the TagBuilder.

   ...

   var attribute = propInfo.GetCustomAttributes(typeof(StringLengthAttribute),false)
                           .OfType()
                           .FirstOrDefault();
   var length = attribute != null ? attribute.MaximumLength : 20; //provide a default
   builder.Attributes.Add("maxlength",length);

   ...

   return new MvcHtmlString( builder.ToString( TagRenderMode.SelfClosing ) );
}

_{See my comment on why I think this is a bad idea.}