Asp.net MVC源码分析--Model Validation(Client端)实现(1)(3)

6                 @Html.ValidationMessageFor(m => m.UserName)
7 </div>
复制代码
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));
复制代码
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) {