altinoren.com - Castle

Using Castle Validators with ASP.NET MVC Model Binders for Automatic Validation

Gokhan Altinoren — Mon, 10 Nov 2008 10:40:43 GMT

I'm sure someone did this before, but I'm too lazy to search for it :)

Model Binders in MVC is a cool concept to map your form values to parameter objects of your Action. There's also this automatic error message display capabilities in MVC. All explained by The Gu here.

Here's my take on validating a model object during the binding process. Castle project has a validation framework and a range of validators which can be used standalone. It would be cool to use it with MVC to ease the validation pain a bit, huh?

First, we need a binder to validate the object using Castle's ValidatorRunner:

    using System.Web.Mvc;

    using Castle.Components.Validator;

    public class ValidatingModelBinder
: DefaultModelBinder

        public override ModelBinderResult
BindModel(ModelBindingContext bindingContext)

            var result = base.BindModel(bindingContext);

            if (result != null &&
result.Value != null)

                var runner = new ValidatorRunner(new CachedValidationRegistry());

                if (!runner.IsValid(result.Value))

                    var summary = runner.GetErrorSummary(result.Value);

                    foreach (var invalidProperty in summary.InvalidProperties)

                        foreach (var error in summary.GetErrorsForProperty(invalidProperty))

                            bindingContext.ModelState.AddModelError(bindingContext.ModelName + "." +
invalidProperty, error);

            return result;

And an object to validate:

    using Castle.Components.Validator;

    public class CreateUser

        [ValidateNonEmpty("Please enter user name.")]

        public string UserName
{ get; set; }

        [ValidateNonEmpty("Please enter password.")]

        public string Password
{ get; set; }

        [ValidateEmail("Email is not valid.")]

        [ValidateNonEmpty("Please enter email address.")]

        public string Email
{ get; set; }

And an action to use the object:

        public ActionResult CreateUser(CreateUser
createUser)

            if (ViewData.ModelState.IsValid)

                ViewData["Message"] = "Done.";

            return View();

Please note that, when the action is invoked, parameter is already validated. We just check ViewData.ModelState.IsValid and act accordingly.

Next, we'll tell the MVC engine to bind CreateUser objects through ValidatingModelBinder, in Application_Start() of Global.asax.cs:

        ModelBinders.Binders.Add(typeof(CreateUser), new ValidatingModelBinder());

So, whenever the engine is bindign to a CreateUser, our binder will execute (and validate) the object. Finally, code below for the view:

<asp:Content ID="Content1" ContentPlaceHolderID="MainContent" runat="server">

    <%if (ViewData["Message"]
!= null)

{%>

        <%=ViewData["Message"]%>

    <%} %>

    <%=Html.ValidationSummary() %>

    <form method="post" action="/Home/CreateUser">

        User name: <br />

        <%=Html.TextBox("CreateUser.UserName")%> <%=Html.ValidationMessage("CreateUser.UserName", "*")%><br />

        Password: <br />

        <%=Html.Password("CreateUser.Password")%> <%=Html.ValidationMessage("CreateUser.Password", "*")%><br />

        Email: <br />

        <%=Html.TextBox("CreateUser.Email")%> <%=Html.ValidationMessage("CreateUser.Email", "*")%><br />

        <input type="submit" value="Submit" />

    </form>

</asp:Content>

Here's the result:

How to Generate NHibernate Configuration Using ActiveWriter

Gokhan Altinoren — Thu, 14 Jun 2007 11:46:32 GMT

Preview 3 has this functionality, but there are a few things to mention.

ActiveWriter use ActiveRecord assembly to generate NHibernate config files. So you'll need Castle.ActiveRecord.dll, NHibernate.dll and all necessary dependincies to make it work.

Set the target to NHibernate
This way, AW will generate .hbm.xml files for each entity in your model.
Set the Assembly Path to where Castle.ActiveRecord.dll, NHibernate.dll and all necessary dependincies reside.
The design decision was that, I didn't want to package these assemblies with AW. Rather than that, I thought user will most probably have them so they can choose whatever version they want to generate the configuration. If you don't supply the path, AW (VS, actually) will look for them in GAc and then {Your VS Path}\Common7\IDE\Castle.ActiveRecord.dll, so if you have them in one of those places, it should be fine.

One other quirk is, if you first try to generate with the wrong path, setti ng the correct one later won't work until you restart Visual Studio. This is the framework's limitation, once you try to load an assembly and get an error, the result will be cached for subsequent tries. So VS appdomain should be restarted to make it work. I'll have a possible soliton for this for a future version of ActiveWriter (will try to load in a dummy appdomain, then in the VS appdomain)

You may use the fully qualified assembly names for Active Record Assembly Name and NHibernate Assembly Name to target a specific version in the GAC, if you have more than one in there.
When you save the model, AW will generate configuration.

I'll prepare a better documentation in the wiki.

Have fun.

Update:

AW does not work with release version of Castle assemblies (RC2?) for NHibernate generation, it works with the trunk (or with recently compiled assemblies). You can use the latest bits from the build server: http://builds.castleproject.org/cruise/index.castle

Fresh from the trunk: ActiveWriter Preview 3

Gokhan Altinoren — Thu, 14 Jun 2007 08:29:25 GMT

This was sitting on the trunk for a while because of a bug in NHibernate config generation. I believe it's fixed now, so let's see if it works :)

First of all, this release is trying to be compatible with Castle trunk, it may generate code usable by released Castle components but it follows recent changes (might miss a few days). You know, Castle will be 1.0 one day and ActiveWriter will be a release, not a preview, in that day.

And I'm trying create some documentation on using.castleproject.org (Castle's wiki) to make Hammett stop whining about the lack of documentation of contrib projects (kidding!). If you're using ActiveWriter and want to share your tips, tricks, workarounds or anything about it, it would be great if you contribute to the documentation.

The most important update is the direct NHibernate configuration support. Now you can instruct ActiveWriter to generate NHibernate configuration files (.hbm.xml) for each entity in your model. Generated classes won't have ActiveRecord attributes in this case. More on this in a later post (Update: here).

Another interesting change is the use of Castle.Components.Validator instead of the ActiveRecord validators. AR changed in the trunk to use it, so does ActiveWriter.

One more exiciting news is, you can drag tables of MySQL from Server Explorer onto the modelin surface (see Michael's patch below).

Full list of changes below. A big thanks to all who sent patches, ideas and bug reports.

New:

Now optionally generates NHibernate hbm.xml files.
Namespace in generated code is now customizable (Idea: Robert van Hoornaar)
Imports in generated code is now customizable (Idea: Robert van Hoornaar)
Model classes can override model level base class definition. (Patch: Robert van Hoornaar)
Model classes can override model level generics generation. (Idea: Robert van Hoornaar)
Contrib-26: Add support for AR Nested / NH Component mappings. Allow the ability to specify a column prefix for active record. (thx: Adam Tybor)
Optionally generates classes implementing INotifyPropertyChanged.
Support for drag-drop from Server Explorer for MySQL databases. Requires MySQL Connector/Net (5.1) (included). (Patch: Michael Morton)
Support for custom types through IUserType. See http://support.castleproject.org/browse/CONTRIB-28#action_11456 for usage. (Patch: Ricardo Stuven)
Ability to define a nested class with a different property name than the nested class (Idea: Craig Neuwirt)

Fixed:

Contrib-23: Produces CascadeEnum instead of ManyRelationCascadeEnum
Ability to generate virtual properties to support Lazy properly (thx: Ayende)
Make sure that Char and AnsiChar types are treated as a System.String types, instead of System.Char types (patch: Ayende)
HasAndbelongToMany does not take custom property names and not found behavior into account.
Can’t add a Many To Many relationship to 2 entities when the Class and Table names are different.
Column keys in many-to-one relations is not optional. (Patch: Robert van Hoornaar)
Partially fixing NHibernate code generation errors. Now works with a workaround.
Nullable types only when NotNull=false (Patch: Ricardo Stuven)
Changed to Castle.Components.Validator

And just one more thing. Someone asked me if ActiveWriter is a competitor for Linq to SQL. AW is just a servent of the heavyweight champion, NHibernate/AR combo. Linq to SQL is competing with NHibernate. I didn't have time to examine Linq to SQL designer, but it's built using DSL Tools just like ActiveWriter so some functionality should be alike. Other than that it's the framework, not the tools, important.

Designers for ORM Tools?

Gokhan Altinoren — Wed, 09 May 2007 14:42:35 GMT

Ayende, in his post on virtual entry barriers / learning curve of Castle pieces, said:

One of the main differences between OSS and Commercial software is the amount of time that is invested in the frills. Active Record and NHibernate has a designer, which is nice, but it is not a level 1 priority to any of the people using either Active Record or NHibernate. The reason is that both those frameworks were built knowing that a designer is not something that you should need in order to work with them.

That is, of course, super true for MonoRail and when I started working on ActiveWriter, I said "ActiveRecord is so simple, no one gonna use a code generator for it". Now I think somewhat different, in the context of O/RM designers.

When I think of working with ActiveRecord, I see it in two different parts. First is the sceleton of an entity; all the attributes tagging the class, properties and fields to describe the model to ActiveRecord and then NHibernate, eventually.

    [ActiveRecord()]

    public partial class Entity
: ActiveRecordBase {

        private int _key;

        [PrimaryKey(PrimaryKeyType.Native, ColumnType="Int32")]

        public int Key
{

            get {

                return this._key;

            }

            set {

                this._key
= value;

            }

        }

    }

This code is a no brainer to write and AR has quite good documentation to get you there easily. But it's so repetative that it's the perfect place for using a designer. I don't say that people using ActiveRecord should forget all the attributes to define an entity alltogether, but once you studied the underlying workings of the framework I believe even the most basic framework can use a designer when it comes to the brute force part of the code. After all, you are designing some entitities and that's what a designer do best.

One problem here is that it's not easy to modify this kind of generated code. Thanks to 2.0, partial classes help great when adding new functionality, but it's impossible to modify generated getters and setters. DSL Tools is using the term "double derived" for the approach used to solve this problem, use an inherited empty entity instead of the original one around to make it possible to override properties. This model works fine in DSL Tools context but might make real world entities complicated. This one and solutions like this which makes code more bloated are, I believe, the dark side of code generating designers.

There is also the process of giving the entity some brains; validation, query helper etc. I, again, can see the value of a designer here. ActiveWriter can generate entities with ActiveRecord validators (and there's a JIRA entry waiting to port it to Castle validators). Thanks to his permission, I'll integrate Ayende's Generator into ActiveWriter to make it generate code with all the typed query functionality but ActiveWriter of course won't be writing the query.

The other part of working with ActiveRecord is knowing what the framework gives you, what does it do on behalf, what are the list of things to know beforehand to know before it starts persisting. You should know about lazy loading, order of saving, inverse relations etc. This is the point when you instruct the framework to manage what you designed before, and I think where a designer should keep it's hands off. ActiveWriter, and tools alike, should help developers to define metadata. They should not act like metadata manipulators to do the programming. I consider Ayende's comments above true in this part of the usage. A good O/RM designer should work without getting the way, and shouldn't make the user careless by doing the thinking on behalf.

Two Screencasts Featuring ActiveWriter

Gokhan Altinoren — Wed, 25 Apr 2007 08:57:28 GMT

Both about MonoRail, actually.

Colin talks about two Castle Contrib projects, CodeGenerator and ActiveWriter: His Screencast Five.
Ayende talks about MonoRail and differences between MR and Web Forms: His Hibernating Rhinos #2.

Seeing your work used in screencasts is priceless.

ActiveWriter Source Moved to Castle Contrib Repository

Gokhan Altinoren — Mon, 12 Mar 2007 10:11:10 GMT

I was using a private SVN for ActiveWriter and thanks to Hammet, the source is now available through Castle Contrib Repository.
Having source on an open repository is great. AW now has it's own Ohloh page :)

Codebase: 27,938 LOC (Most of them generated by DSL Tools, actually:)
Effort (est.): 7 Person Years
Project Cost: $362,806

I feel good! :)

Castle Project is close to RTM

Gokhan Altinoren — Wed, 01 Nov 2006 19:58:57 GMT

Go visit www.castleproject.org and get the lates bits.

The amount of information there is increadible, MonoRail getting started docs are extremely helpful for me. After seeing "Getting Started with ActiveRecord" topic, you will have no excuse not to use ActiveRecord in your next project. And API documentation is just what I need for ActiveWriter's properties window documentation :)

The question is, will I manage to release something new with ActiveWriter to celebrate the Castle release and the hard work these guys doing? Let's see:

Although implementing the toolwindow above turned out to be harder than I thought, I was actually referring to generics support in ActiveWriter, which is still waiting my attention. So, I'll try to hurry++ and sleep--;