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copied!<h1>Update</h1> <p>In addition to the class shown below, I've done a similar thing for <code>IValidatableObject</code> implementations as well <strike>(short notes towards the end of the answer instead of a full code sample because then the answer just gets too long)</strike> - I've added the code for that class as well in response to a comment - it does make the answer <em>very</em> long, but at least you'll have all the code you need.</p> <h1>Original</h1> <p>Since I'm targeting <code>ValidationAttribute</code>-based validation at the moment I researched where MVC creates the <code>ValidationContext</code> that gets fed to the <code>GetValidationResult</code> method of that class.</p> <p>Turns out it's in the <code>DataAnnotationsModelValidator</code>'s <code>Validate</code> method:</p> <pre><code>public override IEnumerable<ModelValidationResult> Validate(object container) { // Per the WCF RIA Services team, instance can never be null (if you have // no parent, you pass yourself for the "instance" parameter). ValidationContext context = new ValidationContext( container ?? Metadata.Model, null, null); context.DisplayName = Metadata.GetDisplayName(); ValidationResult result = Attribute.GetValidationResult(Metadata.Model, context); if (result != ValidationResult.Success) { yield return new ModelValidationResult { Message = result.ErrorMessage }; } } </code></pre> <p>(Copied and reformatted from MVC3 RTM Source)</p> <p>So I figured some extensibility here would be in order:</p> <pre><code>public class DataAnnotationsModelValidatorEx : DataAnnotationsModelValidator { public DataAnnotationsModelValidatorEx( ModelMetadata metadata, ControllerContext context, ValidationAttribute attribute) : base(metadata, context, attribute) { } public override IEnumerable<ModelValidationResult> Validate(object container) { ValidationContext context = CreateValidationContext(container); ValidationResult result = Attribute.GetValidationResult(Metadata.Model, context); if (result != ValidationResult.Success) { yield return new ModelValidationResult { Message = result.ErrorMessage }; } } // begin Extensibility protected virtual ValidationContext CreateValidationContext(object container) { IServiceProvider serviceProvider = CreateServiceProvider(container); //TODO: add virtual method perhaps for the third parameter? ValidationContext context = new ValidationContext( container ?? Metadata.Model, serviceProvider, null); context.DisplayName = Metadata.GetDisplayName(); return context; } protected virtual IServiceProvider CreateServiceProvider(object container) { IServiceProvider serviceProvider = null; IDependant dependantController = ControllerContext.Controller as IDependant; if (dependantController != null && dependantController.Resolver != null) serviceProvider = new ResolverServiceProviderWrapper (dependantController.Resolver); else serviceProvider = ControllerContext.Controller as IServiceProvider; return serviceProvider; } } </code></pre> <p>So I check first for my <code>IDependant</code> interface from the controller, in which case I create an instance of a wrapper class that acts as an adapter between my <code>IDependencyResolver</code> interface and <code>System.IServiceProvider</code>.</p> <p>I thought I'd also handle cases where a controller itself is an <code>IServiceProvider</code> too (not that that applies in my case - but it's a more general solution).</p> <p>Then I make the <code>DataAnnotationsModelValidatorProvider</code> use this validator by default, instead of the original:</p> <pre><code>//register the new factory over the top of the standard one. DataAnnotationsModelValidatorProvider.RegisterDefaultAdapterFactory( (metadata, context, attribute) => new DataAnnotationsModelValidatorEx(metadata, context, attribute)); </code></pre> <p>Now 'normal' <code>ValidationAttribute</code>-based validators, can resolve services:</p> <pre><code>public class ExampleAttribute : ValidationAttribute { protected override ValidationResult IsValid(object value, ValidationContext validationContext) { ICardTypeService service = (ICardTypeService)validationContext.GetService(typeof(ICardTypeService)); } } </code></pre> <p>This still leaves direct <code>ModelValidator</code>-derived needing to be reimplemented to support the same technique - although they already have access to the <code>ControllerContext</code>, so it's less of an issue.</p> <h1>Update</h1> <p>A similar thing has to be done if you want <code>IValidatableObject</code>-implementing types to be able to resolve services during the implementation of <code>Validate</code> without having to keep deriving your own adapters for each type.</p> <ul> <li>Derive a new class from <code>ValidatableObjectAdapter</code>, I called it <code>ValidatableObjectAdapterEx</code></li> <li>from MVCs v3 RTM source, copy the <code>Validate</code> and <code>ConvertResults</code> private method of that class.</li> <li>Adjust the first method to remove references to internal MVC resources, and</li> <li>change how the <code>ValidationContext</code> is constructed</li> </ul> <h1>Update (in response to comment below)</h1> <p>Here's the code for the <code>ValidatableObjectAdapterEx</code> - and I'll point out hopefully more clearly that <code>IDependant</code> and <code>ResolverServiceProviderWrapper</code> used here and before are types that only apply to my environment - if you're using a global, statically-accessible DI container, however, then it should be trivial to re-implement these two classes' <code>CreateServiceProvider</code> methods appropriately.</p> <pre><code>public class ValidatableObjectAdapterEx : ValidatableObjectAdapter { public ValidatableObjectAdapterEx(ModelMetadata metadata, ControllerContext context) : base(metadata, context) { } public override IEnumerable<ModelValidationResult> Validate(object container) { object model = base.Metadata.Model; if (model != null) { IValidatableObject instance = model as IValidatableObject; if (instance == null) { //the base implementation will throw an exception after //doing the same check - so let's retain that behaviour return base.Validate(container); } /* replacement for the core functionality */ ValidationContext validationContext = CreateValidationContext(instance); return this.ConvertResults(instance.Validate(validationContext)); } else return base.Validate(container); /*base returns an empty set of values for null. */ } /// <summary> /// Called by the Validate method to create the ValidationContext /// </summary> /// <param name="instance"></param> /// <returns></returns> protected virtual ValidationContext CreateValidationContext(object instance) { IServiceProvider serviceProvider = CreateServiceProvider(instance); //TODO: add virtual method perhaps for the third parameter? ValidationContext context = new ValidationContext( instance ?? Metadata.Model, serviceProvider, null); return context; } /// <summary> /// Called by the CreateValidationContext method to create an IServiceProvider /// instance to be passed to the ValidationContext. /// </summary> /// <param name="container"></param> /// <returns></returns> protected virtual IServiceProvider CreateServiceProvider(object container) { IServiceProvider serviceProvider = null; IDependant dependantController = ControllerContext.Controller as IDependant; if (dependantController != null && dependantController.Resolver != null) { serviceProvider = new ResolverServiceProviderWrapper(dependantController.Resolver); } else serviceProvider = ControllerContext.Controller as IServiceProvider; return serviceProvider; } //ripped from v3 RTM source private IEnumerable<ModelValidationResult> ConvertResults( IEnumerable<ValidationResult> results) { foreach (ValidationResult result in results) { if (result != ValidationResult.Success) { if (result.MemberNames == null || !result.MemberNames.Any()) { yield return new ModelValidationResult { Message = result.ErrorMessage }; } else { foreach (string memberName in result.MemberNames) { yield return new ModelValidationResult { Message = result.ErrorMessage, MemberName = memberName }; } } } } } } </code></pre> <h1>End Code</h1> <p>With that class in place, you can register this as the default adapter for <code>IValidatableObject</code> instances with the line:</p> <pre><code>DataAnnotationsModelValidatorProvider. RegisterDefaultValidatableObjectAdapterFactory( (metadata, context) => new ValidatableObjectAdapterEx(metadata, context) ); </code></pre>

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