前两篇我们介绍了ModelValidatoin Server 端的实现,那么我们知道在Web.config 中如果我们把ClientValidationEnabled 设置为true时，那么客户端也可以支持表单验证了. 那么这部份功能是如果实现的呢？今天让我们来一起学习Model validation client 端的实现.
一.ModelClientValidationRule类
这个类定义了如何输出客户端的一些信息:
- ErrorMessage:取得或设定用户端验证规则的错误讯息。
- ValidationParameters:取得验证参数清单。
- ValidationType:取得或设定验证类型。
1 public class ModelClientValidationRule {
2
3 private readonly Dictionary<string, object> _validationParameters = new Dictionary<string, object>();
4 private string _validationType;
5
6 public string ErrorMessage {
7 get;
8 set;
9 }
10
11 public IDictionary<string, object> ValidationParameters {
12 get {
13 return _validationParameters;
14 }
15 }
16
17 public string ValidationType {
18 get {
19 return _validationType ?? String.Empty;
20 }
21 set {
22 _validationType = value;
23 }
24 }
25 }
我们知道了这个类的数据结构,那么这些数据是如何输出的呢?我们看一下RequiredAttributeAdapter类,在这里定义了有一个GetClientValidationRules方法,这个方法返回了ModelClientValidationRequiredRule对象(包含了Required validation 需要输出到客户端的数据).
1 public class RequiredAttributeAdapter : DataAnnotationsModelValidator<RequiredAttribute> {
2 public RequiredAttributeAdapter(ModelMetadata metadata, ControllerContext context, RequiredAttribute attribute)
3 : base(metadata, context, attribute) {
4 }
5
6 public override IEnumerable<ModelClientValidationRule> GetClientValidationRules() {
7 return new[] { new ModelClientValidationRequiredRule(ErrorMessage) };
8 }
9 }
二.如果让得到自定义Client Validaton 信息?
上面我们介绍了一些系统内置(Required)的Validation 的输出，那么我们如果需要自定义验证规则如果来输出客户端数据呢？前面我们介绍了DataAnnotationsModelValidatorProvider.GetValidators 方法里自定义的验证是通过DefaultAttributeFactory委托来构造的,让我们顺着这个代码来继续我们的思路。
1 internal static DataAnnotationsModelValidationFactory DefaultAttributeFactory =
2 (metadata, context, attribute) => new DataAnnotationsModelValidator(metadata, context, attribute);
让我接下来看一下DataAnnotationsModelValidator.GetClientValidationRules 方法的实现,我们看到下面代码第4行，说明只有我们自定义的ValidationAtribute只有实现了IClientValidatable接口才能够输出客户端数据。
1 public override IEnumerable<ModelClientValidationRule> GetClientValidationRules() {
2 IEnumerable<ModelClientValidationRule> results = base.GetClientValidationRules();
3
4 IClientValidatable clientValidatable = Attribute as IClientValidatable;
5 if (clientValidatable != null) {
6 results = results.Concat(clientValidatable.GetClientValidationRules(Metadata, ControllerContext));
7 }
8
9 return results;
10 }
三.如果输出自定义Client Validaton 信息到浏览器？
以上的分析是我们得到Cient validation 的数据，那么我们怎么输出这些数据到浏览器呢？
一般我们在View 页面中的代码都是这样的:
1 <div class="editor-label">
2 Name
3 </div>
4 <div class="editor-field">
5 @Html.TextBoxFor(m => m.UserName)
6 @Html.ValidationMessageFor(m => m.UserName)
7 </div>
也就是说Client Validaton 信息是通过Html.TextBoxFor方法来输出的，那么我们接下来研究一下这个方法是如何实现的。
在InputExtension.cs 方件的InputHelper方法我们找到了一些与Client Validaton有关的代码片段,下面第9行代码的GetUnobtrusiveValidationAttributes方法就实现了输出。
1 // If there are any errors for a named field, we add the css attribute.
2 ModelState modelState;
3 if (htmlHelper.ViewData.ModelState.TryGetValue(fullName, out modelState)) {
4 if (modelState.Errors.Count > 0) {
5 tagBuilder.AddCssClass(HtmlHelper.ValidationInputCssClassName);
6 }
7 }
8
9 tagBuilder.MergeAttributes(htmlHelper.GetUnobtrusiveValidationAttributes(name, metadata));
GetUnobtrusiveValidationAttributes方法的源码:
1 // Only render attributes if unobtrusive client-side validation is enabled, and then only if we've
2 // never rendered validation for a field with this name in this form. Also, if there's no form context,
3 // then we can't render the attributes (we'd have no <form> to attach them to).
4 public IDictionary<string, object> GetUnobtrusiveValidationAttributes(string name, ModelMetadata metadata) {
5 Dictionary<string, object> results = new Dictionary<string, object>();
6
7 // The ordering of these 3 checks (and the early exits) is for performance reasons.
8 if (!ViewContext.UnobtrusiveJavaScriptEnabled) {
9 return results;
10 }
11
12 FormContext formContext = ViewContext.GetFormContextForClientValidation();
13 if (formContext == null) {
14 return results;
15 }
16
17 string fullName = ViewData.TemplateInfo.GetFullHtmlFieldName(name);
18 if (formContext.RenderedField(fullName)) {
19 return results;
20 }
21
22 formContext.RenderedField(fullName, true);
23
24 IEnumerable<ModelClientValidationRule> clientRules = ClientValidationRuleFactory(name, metadata);
25 bool renderedRules = false;
26
27 foreach (ModelClientValidationRule rule in clientRules) {
28 renderedRules = true;
29 string ruleName = "data-val-" + rule.ValidationType;
30
31 ValidateUnobtrusiveValidationRule(rule, results, ruleName);
32
33 results.Add(ruleName, HttpUtility.HtmlEncode(rule.ErrorMessage ?? String.Empty));
34 ruleName += "-";
35
36 foreach (var kvp in rule.ValidationParameters) {
37 results.Add(ruleName + kvp.Key, kvp.Value ?? String.Empty);
38 }
39 }
40
41 if (renderedRules) {
42 results.Add("data-val", "true");
43 }
44
45 return results;
46 }
HtmlHelper 构造函数源码:
1 public HtmlHelper(ViewContext viewContext, IViewDataContainer viewDataContainer, RouteCollection routeCollection) {
2 if (viewContext == null) {
3 throw new ArgumentNullException("viewContext");
4 }
5 if (viewDataContainer == null) {
6 throw new ArgumentNullException("viewDataContainer");
7 }
8 if (routeCollection == null) {
9 throw new ArgumentNullException("routeCollection");
10 }
11
12 ViewContext = viewContext;
13 ViewDataContainer = viewDataContainer;
14 RouteCollection = routeCollection;
15 ClientValidationRuleFactory = (name, metadata) => ModelValidatorProviders.Providers.GetValidators(metadata ?? ModelMetadata.FromStringExpression(name, ViewData), ViewContext).SelectMany(v => v.GetClientValidationRules());
16 }
最终我们看到在GetUnobtrusiveValidationAttributes方法内部，MVC 调用了ClientValidationRuleFactory委托来得到clientRules对象它的类型是IEnumerable<ModelClientValidationRule>,这样我们在Model上标记的Client Validation数据就输出到了浏览器端。
--------------------------------------风搔分割线-------------------------------------------------
那么通过以上这些分析我们知道了Server 端如何输出Client Validation数据，那么JavaScript是怎么来进行验证的呢？
下一篇我们来分析jquery.validate.unobtrusive.js 的源码，这里面实现了MVC的客户端验证逻辑。
转载请注明出处:http://www.cnblogs.com/RobbinHan/archive/2011/12/19/2293121.html
本文作者: 十一月的雨 http://www.cnblogs.com/RobbinHan