具有自定义验证属性的.NET MVC错误客户端

时间：2014-11-24 18:14:50

标签： c# asp.net-mvc data-annotations validationattribute

我编写了一个非常简单的自定义验证属性来检查字母数字字符串并且它正在服务器端，但是当我尝试在.NET MVC中使用客户端模型验证时，我得到了validationContext的NullReferenceException。我的自定义属性是在MVC应用程序使用的单独类库中编写的。属性和验证器类在这里：

/// <summary>
    /// Custom validation attribute for an alphanumeric string
    /// </summary>
    public class AlphaNumericAttribute : ValidationAttribute
    {
        public AlphaNumericAttribute()
            : base()
        {
            ErrorMessage = ValidationMessages.AlphaNumeric;
        }

        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            var RegExMatch = ValidationExpressions.AlphaNumeric.Match(value.ToString());
            if (!RegExMatch.Success)
            {
                return new ValidationResult(this.FormatErrorMessage(validationContext.DisplayName));
            }
            return null;
        }
    }

    /// <summary>
    /// Custom validator class for the AlphaNumeric attribute defined above.
    /// </summary>
    public class AlphaNumericValidator : DataAnnotationsModelValidator<AlphaNumericAttribute>
    {
        string errorMsg = string.Empty;

        public AlphaNumericValidator(ModelMetadata metadata,
        ControllerContext controllerContext, AlphaNumericAttribute attribute)
            : base(metadata, controllerContext, attribute) 
        {
            errorMsg = attribute.ErrorMessage;
        }

        public override IEnumerable<ModelClientValidationRule> GetClientValidationRules()
        {
            ModelClientValidationRule validationRule = new ModelClientValidationRule();
            validationRule.ValidationType = "alphanumeric";
            validationRule.ErrorMessage = Attribute.FormatErrorMessage(Metadata.DisplayName);
            return new[] { validationRule };
        }
    }

然后我在MVC应用程序中有一个简单的模型类，它使用[AlphaNumeric]装饰器进行数据注释：

[Required, Display(Name = "Product Code"), AlphaNumeric]
        public string ProductCode { get; set; }

最后我让我的控制器传递了模型类，并使用标准的ModelState.IsValid验证方式...... 

[HttpPost]
public ActionResult Index(CreateModel Model)
{
   if (ModelState.IsValid)
   {
      // Do some stuff
   }
   else return View(Model);
}

当我访问我的网络表单并提交时，我会在调用控制器的操作方法之前立即获得空引用异常：

[NullReferenceException: Object reference not set to an instance of an object.]
   LibData.Validation.AlphaNumericAttribute.IsValid(Object value, ValidationContext validationContext) +75
   System.ComponentModel.DataAnnotations.ValidationAttribute.GetValidationResult(Object value, ValidationContext validationContext) +29
   System.Web.Mvc.DataAnnotationsModelValidator.Validate(Object container) +372
   System.Web.Mvc.<Validate>d__1.MoveNext() +393
   System.Web.Mvc.DefaultModelBinder.OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext) +401
   System.Web.Mvc.DefaultModelBinder.BindComplexElementalModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Object model) +123
   System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +2541
   System.Web.Mvc.DefaultModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +633
   System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) +496
   System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor) +199
   System.Web.Mvc.Async.<>c__DisplayClass21.<BeginInvokeAction>b__19(AsyncCallback asyncCallback, Object asyncState) +1680
   System.Web.Mvc.Async.WrappedAsyncResult`1.CallBeginDelegate(AsyncCallback callback, Object callbackState) +59
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +151
   System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate`1 endDelegate, Object tag, Int32 timeout) +94
   System.Web.Mvc.Async.AsyncControllerActionInvoker.BeginInvokeAction(ControllerContext controllerContext, String actionName, AsyncCallback callback, Object state) +559
   System.Web.Mvc.Controller.<BeginExecuteCore>b__1c(AsyncCallback asyncCallback, Object asyncState, ExecuteCoreState innerState) +82
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallBeginDelegate(AsyncCallback callback, Object callbackState) +73
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +151
   System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object callbackState, BeginInvokeDelegate`1 beginDelegate, EndInvokeVoidDelegate`1 endDelegate, TState invokeState, Object tag, Int32 timeout, SynchronizationContext callbackSyncContext) +105
   System.Web.Mvc.Controller.BeginExecuteCore(AsyncCallback callback, Object state) +588
   System.Web.Mvc.Controller.<BeginExecute>b__14(AsyncCallback asyncCallback, Object callbackState, Controller controller) +47
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallBeginDelegate(AsyncCallback callback, Object callbackState) +65
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +151
   System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object callbackState, BeginInvokeDelegate`1 beginDelegate, EndInvokeVoidDelegate`1 endDelegate, TState invokeState, Object tag, Int32 timeout, SynchronizationContext callbackSyncContext) +139
   System.Web.Mvc.Controller.BeginExecute(RequestContext requestContext, AsyncCallback callback, Object state) +484
   System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.BeginExecute(RequestContext requestContext, AsyncCallback callback, Object state) +50
   System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__4(AsyncCallback asyncCallback, Object asyncState, ProcessRequestState innerState) +98
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallBeginDelegate(AsyncCallback callback, Object callbackState) +73
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +151
   System.Web.Mvc.Async.AsyncResultWrapper.Begin(AsyncCallback callback, Object callbackState, BeginInvokeDelegate`1 beginDelegate, EndInvokeVoidDelegate`1 endDelegate, TState invokeState, Object tag, Int32 timeout, SynchronizationContext callbackSyncContext) +106
   System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +446
   System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +88
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +50
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +301
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

我在这里缺少什么？如果我使用其他内置数据注释，如正则表达式等，我不会得到此错误。我是否需要在MVC应用程序中注册某种处理程序？我真的很茫然。是的，我可以使用简单的正则表达式验证属性来解决这个问题，但我需要了解问题的根源，因为我有许多更复杂的验证属性要编写，并且想要了解如何正确连接它们。感谢...

1 个答案:

答案 0 :(得分：0)

Rick，你需要一些额外的东西才能在客户端工作。 以下是有关如何实现此问题的详细教程：http://thewayofcode.wordpress.com/tag/custom-unobtrusive-validation/

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