Custom Model Binder Not Validating Model - asp.net-mvc

I started to play around with knockout.js and in doing so I used the FromJsonAttribute (created by Steve Sanderson). I ran into an issue with the custom attribute not performing model validation. I put together a simple example-- I know it looks like a lot of code-- but the basic issue is how to force the validation of the model within a custom model binder.
using System.ComponentModel.DataAnnotations;
namespace BindingExamples.Models
{
public class Widget
{
[Required]
public string Name { get; set; }
}
}
and here is my controller:
using System;
using System.Web.Mvc;
using BindingExamples.Models;
namespace BindingExamples.Controllers
{
public class WidgetController : Controller
{
public ActionResult Index()
{
return View();
}
[HttpPost]
public ActionResult Index(Widget w)
{
if(this.ModelState.IsValid)
{
TempData["message"] = String.Format("Thanks for inserting {0}", w.Name);
return RedirectToAction("Confirmation");
}
return View(w);
}
[HttpPost]
public ActionResult PostJson([koListEditor.FromJson] Widget w)
{
//the ModelState.IsValid even though the widget has an empty Name
if (this.ModelState.IsValid)
{
TempData["message"] = String.Format("Thanks for inserting {0}", w.Name);
return RedirectToAction("Confirmation");
}
return View(w);
}
public ActionResult Confirmation()
{
return View();
}
}
}
My issue is that the model is always valid in my PostJson method. For completeness here is the Sanderson code for the FromJson attribute:
using System.Web.Mvc;
using System.Web.Script.Serialization;
namespace koListEditor
{
public class FromJsonAttribute : CustomModelBinderAttribute
{
private readonly static JavaScriptSerializer serializer = new JavaScriptSerializer();
public override IModelBinder GetBinder()
{
return new JsonModelBinder();
}
private class JsonModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var stringified = controllerContext.HttpContext.Request[bindingContext.ModelName];
if (string.IsNullOrEmpty(stringified))
return null;
var model = serializer.Deserialize(stringified, bindingContext.ModelType);
return model;
}
}
}
}

Description
The FromJsonAttribute only binds to the model and does, like you said, no validation.
You can add validation to the FromJsonAttribute in order to validate the model's against his DataAnnotations attributes.
This can be done using the TypeDescriptor class.
TypeDescriptor Provides information about the characteristics for a component, such as its attributes, properties, and events.
Check out my solution. I have tested it.
Solution
private class JsonModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var stringified = controllerContext.HttpContext.Request[bindingContext.ModelName];
if (string.IsNullOrEmpty(stringified))
return null;
var model = serializer.Deserialize(stringified, bindingContext.ModelType);
// DataAnnotation Validation
var validationResult = from prop in TypeDescriptor.GetProperties(model).Cast<PropertyDescriptor>()
from attribute in prop.Attributes.OfType<ValidationAttribute>()
where !attribute.IsValid(prop.GetValue(model))
select new { Propertie = prop.Name, ErrorMessage = attribute.FormatErrorMessage(string.Empty) };
// Add the ValidationResult's to the ModelState
foreach (var validationResultItem in validationResult)
bindingContext.ModelState.AddModelError(validationResultItem.Propertie, validationResultItem.ErrorMessage);
return model;
}
}
More Information
TypeDescriptor Class
System.ComponentModel.DataAnnotations Namespace

Thank you, thank you, dknaack!! Your answer was exactly what I was looking for, except I want to validate after each property is bound b/c I have properties that are dependent on other properties, and I don't want to continue binding if a dependent property is invalid.
Here's my new BindProperty overload:
protected override void BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor){
// if this is a simple property, bind it and return
if(_simplePropertyKeys.ContainsKey(propertyDescriptor.Name)){
this.BindSimpleProperty(bindingContext, propertyDescriptor);
// if this is complex property, only bind it if we don't have an error already
} else if (bindingContext.ModelState.IsValid){
this.BindComplexProperty(bindingContext, propertyDescriptor);
}
// add errors from the data annotations
propertyDescriptor.Attributes.OfType<ValidationAttribute>()
.Where(a => a.IsValid(propertyDescriptor.GetValue(bindingContext.Model)) == false)
.ForEach(r => bindingContext.ModelState.AddModelError(propertyDescriptor.Name, r.ErrorMessage));
}

First of all, I'm only starting to learn ASP.NET so don't take my solution seriously. I found this article and as you, tried to do a custom model binder. There was no validation. Then i just replaced IModelBinder interface with DefaultModelBinder and voula, it works. Hope I could help someone

Related

Using HtmlString throws an InvalidOperationException when updating the model

I'm using an HtmlString property on my model like this
public HtmlString Html { get; set; }
then I have an EditorTemplate that renders and html editor but when I use TryUpdateModel() I get an InvalidOperationException because no type converter can convert between these types String and HtmlString.
Do I need to create a custom model binder or is there another way?
UPDATE:
I'm trying to use HtmlString on my model, mostly for making it obvious that it contains HTML.
So this is what my complete model looks like:
public class Model {
public HtmlString MainBody { get; set; }
}
and this is how I render the form:
#using (Html.BeginForm("save","home")){
#Html.EditorForModel()
<input type="submit" name="submit" />
}
I have created my own editor template called Object.cshtml so that the field MainBody can be rendered as a textarea.
My controller has a Save method that looks like this:
public void Save([ModelBinder(typeof(FooModelBinder))]Model foo) {
var postedValue = foo.MainBody;
}
As you can see I have been playing around with a custom model binder that looks like this:
public class FooModelBinder : DefaultModelBinder {
protected override object GetPropertyValue(ControllerContext controllerContext, ModelBindingContext bindingContext, System.ComponentModel.PropertyDescriptor propertyDescriptor, IModelBinder propertyBinder) {
if (propertyDescriptor.PropertyType == typeof(HtmlString)) {
return new HtmlString(controllerContext.HttpContext.Request.Form["MainBody.MainBody"]);
}
return null;
}
}
this works as expected but I don't know how to get the complete ModelName from the bindingContext because bindingContext.ModelName only contains the MainBody and not MainBody.MainBody?
I'm also interested in other solutions regarding this or maybe if someone thinks it's a really bad idea.
Do I need to create a custom model binder
Yes, if you want to use an HtmlString property on your view model because this class has no parameterless constructor and the default model binder has no clue how to instantiate it.
or is there another way?
Yes, don't use HtmlString property on the view model. There might also be other ways. Unfortunately since you have provided strictly 0 information about your context and what precisely you are trying to achieve that's all we could help you with so far.
UPDATE:
Now that you have shown a wee-bit of your code here's a sample.
Model:
public class Model
{
public HtmlString MainBody { get; set; }
}
Controller:
public class HomeController : Controller
{
public ActionResult Index()
{
return View(new Model());
}
[HttpPost]
public ActionResult Index([ModelBinder(typeof(FooModelBinder))]Model foo)
{
var postedValue = foo.MainBody;
return Content(postedValue.ToHtmlString(), "text/plain");
}
}
Model binder:
public class FooModelBinder : DefaultModelBinder
{
protected override object GetPropertyValue(ControllerContext controllerContext, ModelBindingContext bindingContext, System.ComponentModel.PropertyDescriptor propertyDescriptor, IModelBinder propertyBinder)
{
if (propertyDescriptor.PropertyType == typeof(HtmlString))
{
return new HtmlString(bindingContext.ValueProvider.GetValue(bindingContext.ModelName).AttemptedValue);
}
return null;
}
}
View (~/Views/Home/Index.cshtml):
#using (Html.BeginForm())
{
#Html.EditorForModel()
<input type="submit" name="submit" />
}
Custom object editor template in order to do a deep dive (~/Views/Shared/EditorTemplates/Object.cshtml):
#foreach (var property in ViewData.ModelMetadata.Properties.Where(x => x.ShowForEdit))
{
if (!string.IsNullOrEmpty(property.TemplateHint))
{
#Html.Editor(property.PropertyName, property.TemplateHint)
}
else
{
#Html.Editor(property.PropertyName)
}
}
Custom editor template for the HtmlString type to be rendered as a textarea (~/Views/Shared/EditorTemplates/HtmlString.cshtml):
#Html.TextArea("")
By the way I still don't understand why you would want to use HtmlString as a property instead of a simple string but anyway.

Escape Certain Characters On Model Property in ASP.NET MVC

Can I create an attribute that will let me modify the value of it in my ASP.NET MVC Model? It relates to this question below where '%' is being sent to the database, but I would like a generic way to escape certain characters with the data comes from the UI. I know you can validate properties, but can you modify them on the SET?
MySQL and LIKE comparison with %
[Clean]
public string FirstName { get; set; }
[Clean]
public string LastName{ get; set; }
Does this have a lot of value over just calling a clean method in the setter for each property? I worry that even if this were possible, it would introduce a lot of complexity depending on what the expected behavior was.
My suggestion is to just make a function and call it from the setter instead.
I think your Attribute should be at the class level to get access to this class properties
Lets say :
[AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = true)]
public class ClearAttribute : ValidationAttribute
{
private string[] wantedProperties;
public ClearAttribute(params string[] properties)
{
wantedProperties = properties;
}
public override object TypeId
{
get { return new object(); }
}
public override bool IsValid(object value)
{
PropertyInfo[] properties = value.GetType().GetProperties();
foreach (PropertyInfo property in properties)
{
if (wantedProperties.Contains(property.Name))
{
var oldValue = property.GetValue(value, null).ToString();
var newValue = oldValue + "Anything you want because i don't know a lot about your case";
property.SetValue(value, newValue, null);
}
}
return true;
}
}
And the usage should be:
[Clear("First")]
public class TestMe{
public string First {get; set;}
public string Second {get; set;}
}
Hope this helped :)
All you have to do is create a Custom Model Binder and override the SetProperty method to do the clean up.
public class CustomModelBinder: DefaultModelBinder
{
protected override void SetProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor, object value)
{
if (propertyDescriptor.Attributes.Contains(new Clean()) && propertyDescriptor.PropertyType == typeof(string))
{
value = value != null ? ((string)value).Replace("%", "") : value;
}
base.SetProperty(controllerContext, bindingContext, propertyDescriptor, value);
}
}
You can employ any of these options to use your custom model binder.
Registering the custom binder for a particular model in Global.asax.cs
ModelBinders.Binders.Add(typeof(MyModel), new CustomModelBinder());
Registering the custom binder in action parameter
public ActionResult Save([ModelBinder(typeof(CustomModelBinder))]MyModel myModel)
{
}
Registering the custom binder as the default model binder.
ModelBinders.Binders.DefaultBinder = new CustomModelBinder();

One custom model binder to CreateModel and another to BindModel?

Background:
In my MVC post back action methods I am receiving command objects rather than view models. The idea is that these command objects (which roughly equate to transaction scripts) will be set up and ready to execute upon entering the action method, with the model binder having set parameters which are used during the execution process:
public class MyCommand : IMyCommand
{
// In this case Value1 and Value2 are being set by the default model binder from posted form values - wonderful :)
public String Value1 { get; set; }
public String Value2 { get; set; }
public CommandResult ExecuteCommand()
{
// Does something awesome...
}
}
To make things a little more complex, my command objects have dependencies (services, repositories etc) which are required in their respective constructors; so I had to create a custom model binder which used the default DependencyResolver (which was already set up with my IoC container) to construct the model objects:
public class DependencyModelBinder : DefaultModelBinder
{
protected override Object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType)
{
return DependencyResolver.Current.GetService(modelType);
}
}
And set up in Global.asax.cs like so:
ModelBinders.Binders.DefaultBinder = new DependencyModelBinder();
Again this all works fine, the dependencies are injected into the constructor and then the default model binder takes over to set the properties as usual.
The Issue:
The problem I have is that all of my command objects have a 'SessionId' GUID parameter (which comes from a cookie), and the first thing they do is try to resolve a session object from this id using an injected service.
public class MyCommand : IMyCommand
{
public MyCommand (ISessionRepository sessionRepository) { ... }
public Guid SessionId { get; set; } // Set by model binder from a cookie...
public CommandResult Execute()
{
Session session = SessionRepository.Get(SessionId);
if (session == null)
// Do something not so awesome...
}
}
I wanted to remove this repetition, so I created a second model binder which would take care of this lookup in the repository, meaning my command objects could have a Session property directly (removing the constructor dependency for the session repository).
public class SessionModelBinder : DefaultModelBinder
{
public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var sessionRepository = DependencyResolver.Current.GetService<ISessionRepository>();
return sessionRepository.Get((Guid)controllerContext.HttpContext.Request["SessionId"]);
}
}
My Global.asax.cs file now looking like so:
ModelBinders.Binders.DefaultBinder = new DependencyModelBinder();
ModelBinders.Binders.Add(typeof(Session), new SessionModelBinder());
Having tested the SessionModelBinder in isolation, I know it works. However when using it in conjunction with the DependencyModelBinder, it is never called. How can I get MVC to use my DependencyModelBinder when constructing model objects, but have it use my SessionModelBinder when binding session properties on them? Or does anyone know a better approach to this?
You could use the GetPropertyValue method in your original model binder to provide a value for the Session property:
public class DependencyModelBinder : DefaultModelBinder
{
protected override object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType)
{
return DependencyResolver.Current.GetService(modelType);
}
protected override object GetPropertyValue(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor, IModelBinder propertyBinder)
{
if (propertyDescriptor.Name == "Session")
{
var sessionRepository = DependencyResolver.Current.GetService<ISessionRepository>();
return sessionRepository.Get(controllerContext.HttpContext.Request["SessionId"]);
}
return base.GetPropertyValue(controllerContext, bindingContext, propertyDescriptor, propertyBinder);
}
}

Bind formValue to property of different name, ASP.NET MVC

I was wondering if there was a way to bind form values passed into a controller that have different Id's from the class properties.
The form posts to a controller with Person as a parameter that has a property Name but the actual form textbox has the id of PersonName instead of Name.
How can I bind this correctly?
Don't bother with this, just write a PersonViewModel class that reflects the exact same structure as your form. Then use AutoMapper to convert it to Person.
public class PersonViewModel
{
// Instead of using a static constructor
// a better place to configure mappings
// would be Application_Start in global.asax
static PersonViewModel()
{
Mapper.CreateMap<PersonViewModel, Person>()
.ForMember(
dest => dest.Name,
opt => opt.MapFrom(src => src.PersonName));
}
public string PersonName { get; set; }
}
public ActionResult Index(PersonViewModel personViewModel)
{
Person person = Mapper.Map<PersonViewModel, Person>(personViewModel);
// Do something ...
return View();
}
You could have your own custom model binder for that model.
public class PersonBinder : IModelBinder {
public object BindModel(ControllerContext controllerContext,
ModelBindingContext bindingContext) {
return new Person { Name =
controllerContext.HttpContext.Request.Form["PersonName"] };
}
}
And your action :
public ActionResult myAction([ModelBinder(typeof(PersonBinder))]Person m) {
return View();
}

ASP.NET MVC UpdateModel with interface

I am trying to get UpdateModel to populate a model that is set as only an interface at compile-time. For example, I have:
// View Model
public class AccountViewModel {
public string Email { get; set; }
public IProfile Profile { get; set; }
}
// Interface
public interface IProfile {
// Empty
}
// Actual profile instance used
public class StandardProfile : IProfile {
public string FavoriteFood { get; set; }
public string FavoriteMusic { get; set; }
}
// Controller action
public ActionResult AddAccount(AccountViewModel viewModel) {
// viewModel is populated already
UpdateModel(viewModel.Profile, "Profile"); // This isn't working.
}
// Form
<form ... >
<input name='Email' />
<input name='Profile.FavoriteFood' />
<input name='Profile.FavoriteMusic' />
<button type='submit'></button>
</form>
Also note that I have a custom model binder that inherits from DefaultModelBinder being used that populates IProfile with an instance of StandardProfile in the overriden CreateModel method.
The problem is that FavoriteFood and FavoriteMusic are never populated. Any ideas? Ideally this would all be done in the model binder, but I'm not sure it is possible without writing a completely custom implementation.
Thanks, Brian
I would have to check the ASP.NET MVC code (DefaultModelBinder) but I'm guessing that its reflecting on the type IProfile, and not the instance, StandardProfile.
So it looks for any IProfile members it can try to bind, but its an empty interface, so it considers itself done.
You could try something like updating the BindingContext and changing the ModelType to StandardProfile and then calling
bindingContext.ModelType = typeof(StandardProfile);
IProfile profile = base.BindModel(controllerContext, bindingContext);
Anyways, having an empty Interface is weird~
Edit: just want to add that code above is just pseudo code, you would need to check DefaultModelBinder to see exactly what you want to write.
Edit#2:
Can you do:
public class ProfileModelBinder : DefaultModelBinder
{
public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) {
{
bindingContext.ModelType = typeof(StandardProfile);
return base.BindModel(controllerContext, bindingContext);
}
}
No need to make a model binder for AccountView, that one works fine.
Edit #3
Tested it out, the above binder works, just need to add:
ModelBinders.Binders[typeof(IProfile)] = new ProfileModelBinder();
Your action looks like:
public ActionResult AddAccount(AccountViewModel viewModel) {
// viewModel is fully populated, including profile, don't call UpdateModel
}
You can use IOC when setting the model binder (have the type constructor injected for instance).
Not inspecting the actual type behind the interface was discussed here: http://forums.asp.net/t/1348233.aspx
That said, I found a hackish way around the problem. Since I already had a custom model binder for this type, I was able to add some code to it to perform the binding for me. Here's what my model binder looks like now:
public class AccountViewModelModelBinder : DefaultModelBinder
{
private readonly IProfileViewModel profileViewModel;
private bool profileBound = false;
public AccountViewModelModelBinder(IProfileViewModel profileViewModel)
{
this.profileViewModel = profileViewModel;
}
protected override void OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
// Bind the profile
if (profileBound)
return;
profileBound = true;
bindingContext.ModelType = profileViewModel.GetType();
bindingContext.Model = profileViewModel;
bindingContext.ModelName = "Profile";
BindModel(controllerContext, bindingContext);
}
protected override object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, System.Type modelType)
{
var model = new AccountViewModel();
model.Profile = profileViewModel;
return model;
}
}
Basically, when the model binder is "done" binding the main AccountViewModel, I then alter the binding context (as suggested by eyston) and call BindModel once again. This then binds my profile. Note that I called GetType on the profileViewModel (which is supplied by the IOC container in the constructor). Also notice that I include a flag to indicate if the profile model has been bound already. Otherwise there would be an endless loop of OnModelUpdated being called.
I'm not saying this is pretty, but it does work well enough for my needs. I'd still love to hear about other suggestions.

Resources