altinoren.com - .Net

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:

Generating Code? Wear a CodeDom

Gokhan Altinoren — Mon, 28 Aug 2006 21:46:29 GMT

I use CodeDom to generate ActiveRecord classes in ActiveWriter. Quite fancy, but gets complicated easily. To generate something like this:

        public override bool Equals(object obj)

        {

            if (obj
== this) return true;

            if (obj
== null || obj.GetType() != this.GetType()) return false;

            MyCompositeKey test
= (MyCompositeKey)obj;

            return (_keyA
== test.KeyA || (_keyA != null && _keyA.Equals(test.KeyA)))
&&

              (_keyB == test.KeyB
|| (_keyB != null && _keyB.Equals(test.KeyB)));

        }

you code this:

        private CodeTypeMember GetCompositeClassEqualsMethod(string className,  List<CodeMemberField>
fields)

        {

            CodeMemberMethod equals
= new CodeMemberMethod();

            equals.Attributes = MemberAttributes.Public
| MemberAttributes.Override;

            equals.ReturnType = new CodeTypeReference(typeof(Boolean));

            equals.Name = "Equals";

            CodeParameterDeclarationExpression param
= new CodeParameterDeclarationExpression(typeof(Object), "obj");

            equals.Parameters.Add(param);

            equals.Statements.Add(new CodeConditionStatement(

                  new CodeBinaryOperatorExpression(

  new CodeFieldReferenceExpression(null, "obj"),

  CodeBinaryOperatorType.ValueEquality, new CodeThisReferenceExpression()

  ), new CodeMethodReturnStatement(new CodePrimitiveExpression(true))

)

                );

            equals.Statements.Add(new CodeConditionStatement

(

                  new CodeBinaryOperatorExpression

  (

  new CodeBinaryOperatorExpression(

      new CodeFieldReferenceExpression(null, "obj"),

      CodeBinaryOperatorType.ValueEquality, new CodePrimitiveExpression(null)),

  CodeBinaryOperatorType.BooleanOr,

  new CodeBinaryOperatorExpression(

      new CodeMethodInvokeExpression(new CodeFieldReferenceExpression(null, "obj"), "GetType"),

      CodeBinaryOperatorType.IdentityInequality,

      new CodeMethodInvokeExpression(new CodeThisReferenceExpression(), "GetType"))

  )

, new CodeMethodReturnStatement(new CodePrimitiveExpression(false))

)

                );

            equals.Statements.Add(

                new CodeVariableDeclarationStatement(new CodeTypeReference(className), "test",

            new CodeCastExpression(new CodeTypeReference(className),

                new CodeFieldReferenceExpression(null, "obj"))));

            List<CodeExpression>
expressions = new List<CodeExpression>();

            foreach (CodeMemberField field in fields)

            {

                expressions.Add(

                    new CodeBinaryOperatorExpression(

    //_keyA == test.KeyA

    new CodeBinaryOperatorExpression(

        new CodeFieldReferenceExpression(null,
field.Name),

        CodeBinaryOperatorType.ValueEquality,

        new CodeFieldReferenceExpression(new CodeFieldReferenceExpression(null, "test"),
field.Name)),

    CodeBinaryOperatorType.BooleanOr, //
||

    new CodeBinaryOperatorExpression(

        //_keyA != null

        new CodeBinaryOperatorExpression(

            new CodeFieldReferenceExpression(null,
field.Name),

            CodeBinaryOperatorType.IdentityInequality,

            new CodePrimitiveExpression(null)

            ),

        CodeBinaryOperatorType.BooleanAnd, //
&&

        // _keyA.Equals(
test.KeyA )   

        new CodeMethodInvokeExpression(

            new CodeFieldReferenceExpression(null,
field.Name), "Equals",

            new CodeFieldReferenceExpression(

                new CodeFieldReferenceExpression(null, "test"),
field.Name))

        )

    )

);

            }

            CodeExpression expression
= null;

            if (expressions.Count
> 2)

                expression
=

                    new CodeBinaryOperatorExpression(expressions[0], CodeBinaryOperatorType.BooleanAnd,
GetBooleanAnd(expressions, 1));

            else

                expression
= new CodeBinaryOperatorExpression(expressions[0], CodeBinaryOperatorType.BooleanAnd,
expressions[1]);

            equals.Statements.Add(new CodeMethodReturnStatement(expression));

            return equals;

        }

Strangely, there's no CodeBinaryOperatorType.ValueInequality operator defined. (a==b)==false will do the trick, but how about not having an XOR? I find CodeDom's lack of completeness... disturbing.