Bootstrap ASP.NET MVC Validation Summary

MvcHtmlHelper.cs

using System;
using System.Web.Mvc;

namespace Nurvx.Mvc.Helpers
{
    public static class MvcHtmlHelper
    {
        public static MvcHtmlString BootstrapValidationSummary(this HtmlHelper helper, string validationMessage = "", bool dismissible = false)
        {
            // If the ModelState has no errors, return empty
            if (helper.ViewData.ModelState.IsValid)
                return MvcHtmlString.Empty;

            // Create the validation summary div wrapper element
            TagBuilder divValidationSummary = new TagBuilder("div");
            divValidationSummary.MergeAttribute("class", "validation-summary-errors alert alert-danger alert-dismissible");
            divValidationSummary.MergeAttribute("role", "alert");

            // If dismissible add the close button
            if (dismissible)
            {
                // Create the button element for closing
                TagBuilder buttonClose = new TagBuilder("button");
                buttonClose.MergeAttribute("type", "button");
                buttonClose.MergeAttribute("class", "close");
                buttonClose.MergeAttribute("data-dismiss", "alert");

                // Create 'X' span
                TagBuilder spanButtonCloseX = new TagBuilder("span");
                spanButtonCloseX.MergeAttribute("aria-hidden", "true");
                spanButtonCloseX.InnerHtml = "×";

                // Create 'Close' text span
                TagBuilder spanButtonCloseText = new TagBuilder("span");
                spanButtonCloseText.MergeAttribute("class", "sr-only");
                spanButtonCloseText.InnerHtml = "Close";

                // Add both span elements to the button
                buttonClose.InnerHtml = spanButtonCloseX.ToString(TagRenderMode.Normal) + spanButtonCloseText.ToString(TagRenderMode.Normal);

                divValidationSummary.InnerHtml += buttonClose.ToString(TagRenderMode.Normal);
            }

            if (!String.IsNullOrWhiteSpace(validationMessage))
            {
                // If a validation message is specified, add it as bold text
                TagBuilder strongValidationMessage = new TagBuilder("strong");
                strongValidationMessage.InnerHtml = validationMessage;
                divValidationSummary.InnerHtml += strongValidationMessage.ToString(TagRenderMode.Normal);
            }

            // Create the validation messages "ul" element
            TagBuilder ulValidationErrorMessages = new TagBuilder("ul");
            foreach (var key in helper.ViewData.ModelState.Keys)
            {
                foreach (var err in helper.ViewData.ModelState[key].Errors)
                {
                    // Create and add validation message "li" element to the "ul" element
                    TagBuilder liValidationErrorMessage = new TagBuilder("li");
                    liValidationErrorMessage.SetInnerText(helper.Encode(err.ErrorMessage));
                    ulValidationErrorMessages.InnerHtml += liValidationErrorMessage.ToString(TagRenderMode.Normal);
                }
            }

            // Add the ul element to the validation summary div element
            divValidationSummary.InnerHtml += ulValidationErrorMessages.ToString(TagRenderMode.Normal);

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