Edit: This assumes you are using MVC 3. Unfortunately my code is in VB.NET since that's what I have to use at work.
In order to make everything work nicely with the new unobtrusive validation there are a few things you have to do. I powered through them a couple of weeks ago.
First, create a custom attribute class that inherits from ValidationAttribute. A simple RequiredIf attribute class is below:
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
Next, you need to implement a validator class. This class is responsible for letting MVC know the client validation rules that are required for the unobtrusive validation library to work.
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
Now you can register everything in the application start method of Global.asax:
DataAnnotationsModelValidatorProvider.RegisterAdapter(GetType(RequiredIfAttribute), GetType(RequiredIfValidator))
This gets you 90% of the way there. Now you just need to tell JQuery validate and MS's unobtrusive validation layer how to read your new attributes:
/// <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));
Hope this helps, this was a real pain to get working.
