asp.net mvc - How to customize Html.ValidationMessageFor in ASP MVC

Question

Is it possible to customize the Html.ValidationMessageFor method so that it produces different HTML?

I want to do something similar to:

<div class="field-error-box">
    <div class="top"></div>
    <div class="mid"><p>This field is required.</p></div>
</div>

Answer 1

I am not sure if it's possible to use paragraph instead of default span, as it may make impossible for validation plugin to place error messages. But for div -s, thats easy - you could write custom html helper.

Something along these lines (may need further testing/coding). You will need to include the namespace of this static extension method in your view, or put this into System.Web.Mvc.Html directly.

public static class Validator
{
    public static MvcHtmlString MyValidationMessageFor<TModel, TProperty>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TProperty>> expression)
    {
        TagBuilder containerDivBuilder = new TagBuilder("div");
        containerDivBuilder.AddCssClass("field-error-box");

        TagBuilder topDivBuilder = new TagBuilder("div");
        topDivBuilder.AddCssClass("top");

        TagBuilder midDivBuilder = new TagBuilder("div");
        midDivBuilder.AddCssClass("mid");
        midDivBuilder.InnerHtml = helper.ValidationMessageFor(expression).ToString();

        containerDivBuilder.InnerHtml += topDivBuilder.ToString(TagRenderMode.Normal);
        containerDivBuilder.InnerHtml += midDivBuilder.ToString(TagRenderMode.Normal);

        return MvcHtmlString.Create(containerDivBuilder.ToString(TagRenderMode.Normal));
    }
}

As you see, this uses default ValidationMessageFor method, to not interfere with validation-plugin error message processing.

And you use this simply, as default validation message helper

@Html.MyValidationMessageFor(model => model.SomeRequiredField)