Audit ActionFilter in ASP.NET MVC

CustomerController.cs

    public class CustomerController : Controller
    {
        public ViewResult Index()
        {
            return View();
        }

        public ViewResult Edit()
        {
            var existingCustomer = new Customer();
            existingCustomer.Name = "Matthew D. Groves";
            existingCustomer.ShoeSize = 14;
            existingCustomer.Birthday = new DateTime(1980, 1, 29);
            return View(existingCustomer);
        }

        [HttpPost]
        [AuditAttribute(typeof(Customer), "Name", "ShoeSize")]
        public ActionResult Edit(Customer customer)
        {
            if(ModelState.IsValid)
            {
                // put code here to save edited customer to database
                return RedirectToAction("Index");
            }
            return View(customer);
        }
    }

    public class AuditAttribute : ActionFilterAttribute
    {
        readonly Type _typeToAudit;
        readonly string[] _fieldsToAudit;

        public AuditAttribute(Type typeToAudit, params string[] fieldsToAudit)
        {
            _typeToAudit = typeToAudit;
            _fieldsToAudit = fieldsToAudit;
        }

        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            if (filterContext.Controller.ViewData.ModelState.IsValid)
            {
                var auditRecord = new AuditRecord();
                auditRecord.ActionName = filterContext.ActionDescriptor.ActionName;
                auditRecord.ControllerName = filterContext.ActionDescriptor.ControllerDescriptor.ControllerName;
                auditRecord.DateTimeAuditRecorded = DateTime.Now;
                auditRecord.EntityTypeAudited = _typeToAudit.Name;
                auditRecord.User = "nlopez";         // use in reality something like: filterContext.HttpContext.User.Identity.Name

                var parameters = filterContext.ActionDescriptor.GetParameters();
                var parameterToAudit = parameters.SingleOrDefault(p => p.ParameterType == _typeToAudit);
                var argumentToAudit = filterContext.ActionParameters[parameterToAudit.ParameterName];
                var propertiesToAudit = parameterToAudit.ParameterType.GetProperties()
                                        .Where(p => _fieldsToAudit.Contains(p.Name));
                foreach (var propertyInfo in propertiesToAudit)
                {
                    var pi = argumentToAudit.GetType().GetProperty(propertyInfo.Name);
                    var auditValue = pi.GetValue(argumentToAudit, null);
                    auditRecord.AuditedFields[propertyInfo.Name] = auditValue.ToString();
                }
                filterContext.Controller.TempData["AuditValues"] = auditRecord;
            }
            else
            {
                filterContext.HttpContext.Response.Write("Auditing not performed, since submission was not valid.");
            }
        }
    }

    public class Customer
    {
        [Required]
        public string Name { get; set; }
        [Required, Range(1, 20)]
        public int ShoeSize { get; set; }
        [Required]
        public DateTime Birthday { get; set; }
    }

    public class AuditRecord
    {
        public AuditRecord()
        {
            AuditedFields = new Dictionary<string, string>();
        }
        public IDictionary<string, string> AuditedFields { get; private set; }
        public string EntityTypeAudited { get; set; }
        public DateTime DateTimeAuditRecorded { get; set; }
        public string User { get; set; }
        public string ControllerName { get; set; }
        public string ActionName { get; set; }
    }

Edit.cshtml

@model ActionFiltersKitchenSink.Controllers.Customer

@{
    ViewBag.Title = "Edit";
}

<h2>Edit</h2>

@using (Html.BeginForm()) {
    @Html.ValidationSummary(true)
    <fieldset>
        <legend>Customer</legend>

        <div class="editor-label">
            @Html.LabelFor(model => model.Name)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Name)
            @Html.ValidationMessageFor(model => model.Name)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.ShoeSize)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.ShoeSize)
            @Html.ValidationMessageFor(model => model.ShoeSize)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.Birthday)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Birthday)
            @Html.ValidationMessageFor(model => model.Birthday)
        </div>

        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

Index.cshtml

@using ActionFiltersKitchenSink.Controllers;
@{
    ViewBag.Title = "Index";
}

<h2>ActionFilter Audit Demo</h2>

@if (TempData["AuditValues"] != null)
{
    <fieldset>
        <legend>Audit of last transaction</legend>
        <ul>
            <li><strong>Entity type:</strong> @((TempData["AuditValues"] as AuditRecord).EntityTypeAudited)</li>
            <li><strong>Date/time:</strong> @((TempData["AuditValues"] as AuditRecord).DateTimeAuditRecorded)</li>
            <li><strong>User:</strong>  @((TempData["AuditValues"] as AuditRecord).User)</li>
            <li><strong>Controller name:</strong>  @((TempData["AuditValues"] as AuditRecord).ControllerName)</li>
            <li><strong>Action name:</strong>  @((TempData["AuditValues"] as AuditRecord).ActionName)</li>
            <li><strong>Fields</strong>
                <ul>
                @foreach (var kvp in (TempData["AuditValues"] as AuditRecord).AuditedFields)
                {
                    <li><strong>@kvp.Key</strong>: @kvp.Value</li>
                }
                </ul>
            </li>
        </ul>
    </fieldset>
}

<p>Click here to @Html.ActionLink("edit the customer record for Matthew D. Groves", "Edit", "Customer")</p>