编辑：假设您使用的是 MVC 3。不幸的是，我的代码在 VB.NET 中，因为这是我在工作中必须使用的。
为了使新的不显眼的验证能够很好地工作，您需要做一些事情。几周前我通过了它们。
首先，创建一个继承自ValidationAttribute 的自定义属性类。一个简单的RequiredIf属性类如下：
Imports System.ComponentModel
Imports System.ComponentModel.DataAnnotations
<AttributeUsage(AttributeTargets.Field Or AttributeTargets.Property, AllowMultiple:=False, Inherited:=False)> _
Public NotInheritable Class RequiredIfAttribute
Inherits ValidationAttribute
Private Const _defaultErrorMessage As String = "'{0}' is required."
Private ReadOnly _dependentProperty As String
Private ReadOnly _targetValues As Object()
Public Sub New(dependentProperty As String, targetValues As Object())
MyBase.New(_defaultErrorMessage)
_dependentProperty = dependentProperty
_targetValues = targetValues
End Sub
Public Sub New(dependentProperty As String, targetValues As Object(), errorMessage As String)
MyBase.New(errorMessage)
_dependentProperty = dependentProperty
_targetValues = targetValues
End Sub
Public ReadOnly Property DependentProperty() As String
Get
Return _dependentProperty
End Get
End Property
Public ReadOnly Property TargetValues() As Object()
Get
Return _targetValues
End Get
End Property
Public Overrides Function FormatErrorMessage(name As String) As String
Return String.Format(Globalization.CultureInfo.CurrentUICulture, ErrorMessageString, name)
End Function
Protected Overrides Function IsValid(value As Object, context As ValidationContext) As ValidationResult
' find the other property we need to compare with using reflection
Dim propertyValue = context.ObjectType.GetProperty(DependentProperty).GetValue(context.ObjectInstance, Nothing).ToString()
Dim match = TargetValues.SingleOrDefault(Function(t) t.ToString().ToLower() = propertyValue.ToLower())
If match IsNot Nothing AndAlso value Is Nothing Then
Return New ValidationResult(FormatErrorMessage(context.DisplayName))
End If
Return Nothing
End Function
End Class
接下来，您需要实现一个验证器类。这个类负责让 MVC 知道非侵入式验证库工作所需的客户端验证规则。
Public Class RequiredIfValidator
Inherits DataAnnotationsModelValidator(Of RequiredIfAttribute)
Public Sub New(metaData As ModelMetadata, context As ControllerContext, attribute As RequiredIfAttribute)
MyBase.New(metaData, context, attribute)
End Sub
Public Overrides Function GetClientValidationRules() As IEnumerable(Of ModelClientValidationRule)
Dim rule As New ModelClientValidationRule() With {.ErrorMessage = ErrorMessage,
.ValidationType = "requiredif"}
rule.ValidationParameters("dependentproperty") = Attribute.DependentProperty.Replace("."c, HtmlHelper.IdAttributeDotReplacement)
Dim first As Boolean = True
Dim arrayString As New StringBuilder()
For Each param In Attribute.TargetValues
If first Then
first = False
Else
arrayString.Append(",")
End If
arrayString.Append(param.ToString())
Next
rule.ValidationParameters("targetvalues") = arrayString.ToString()
Return New ModelClientValidationRule() {rule}
End Function
End Class
现在你可以在Global.asax的应用程序启动方法中注册一切：
DataAnnotationsModelValidatorProvider.RegisterAdapter(GetType(RequiredIfAttribute), GetType(RequiredIfValidator))
这可以让您完成 90% 的任务。现在你只需要告诉 JQuery validate 和 MS 的不显眼的验证层如何读取你的新属性：
/// <reference path="jquery-1.4.1-vsdoc.js" />
/// <reference path="jquery.validate-vsdoc.js" />
/* javascript for custom unobtrusive validation
==================================================== */
(function ($) {
// this adds the custom "requiredif" validator to the jQuery validate plugin
$.validator.addMethod('requiredif',
function (value, element, params) {
// the "value" variable must not be empty if the dependent value matches
// one of the target values
var dependentVal = $('#' + params['dependentProperty']).val().trim().toLowerCase();
var targetValues = params['targetValues'].split(',');
// loop through all target values
for (i = 0; i < targetValues.length; i++) {
if (dependentVal == targetValues[i].toLowerCase()) {
return $.trim(value).length > 0;
}
}
return true;
},
'not used');
// this tells the MS unobtrusive validation layer how to read the
// HTML 5 attributes that are output for the custom "requiredif" validator
$.validator.unobtrusive.adapters.add('requiredif', ['dependentProperty', 'targetValues'], function (options) {
options.rules['requiredif'] = options.params;
if (options.message) {
options.messages['requiredif'] = options.message;
}
});
} (jQuery));
希望这会有所帮助，开始工作真的很痛苦。