asp.net mvc源码分析-BeginForm方法 和ClientValidationEnabled 属性

 

运行结果就是生成form表单

 

一般我们的表单提交都涉及到强类型，所以一般需要@model MvcApp.Controllers.UserInfo指令，那我们来看看你用@using (Html.BeginForm()) 和Html.BeginForm();、Html.EndForm();这两种用法有什么区别。

我们找到BeginForm返回的是一个MvcForm，而MvcForm的一定如下： public class MvcForm : IDisposable

可见使用using最后调用的是MvcForm的Dispose方法：

 protected virtual void Dispose(bool disposing) {
            if (!_disposed) {
                _disposed = true;
                _writer.Write("</form>");
                // output client validation and restore the original form context
                if (_viewContext != null) {
                    _viewContext.OutputClientValidation();
                    _viewContext.FormContext = _originalFormContext;
                }
            }
        }

这里的_disposed默认是false，_writer是viewContext.Writer或则httpResponse.Output都表示当前的输出流。那么我们再来看看EndForm吧：

 public static void EndForm(this HtmlHelper htmlHelper) {
            htmlHelper.ViewContext.Writer.Write("</form>");
            htmlHelper.ViewContext.OutputClientValidation();
        }

可见EndForm和MvcForm的Dispose方法完全等价。

我们来看看你BeginForm是如何实现的,

 public static MvcForm BeginForm(this HtmlHelper htmlHelper) {
            // generates <form action="{current url}" method="post">...</form>
            string formAction = htmlHelper.ViewContext.HttpContext.Request.RawUrl;
            return FormHelper(htmlHelper, formAction, FormMethod.Post, new RouteValueDictionary());
        }

   public static MvcForm BeginForm(this HtmlHelper htmlHelper, string actionName, string controllerName, RouteValueDictionary routeValues, FormMethod method, IDictionary<string, object> htmlAttributes) {
            string formAction = UrlHelper.GenerateUrl(null /* routeName */, actionName, controllerName, routeValues, htmlHelper.RouteCollection, htmlHelper.ViewContext.RequestContext, true /* includeImplicitMvcValues */);
            return FormHelper(htmlHelper, formAction, method, htmlAttributes);
        }

这里的FormHelper方法比较简单，里面有一句需要注意一下  bool traditionalJavascriptEnabled = htmlHelper.ViewContext.ClientValidationEnabled && !htmlHelper.ViewContext.UnobtrusiveJavaScriptEnabled;这里ClientValidationEnabled 和UnobtrusiveJavaScriptEnabled默认都是true，所以traditionalJavascriptEnabled 为false。

上面有个GenerateUrl方法，这个方法也很简单，关键代码就3句。

RouteValueDictionary mergedRouteValues = RouteValuesHelpers.MergeRouteValues(actionName, controllerName, requestContext.RouteData.Values, routeValues, includeImplicitMvcValues);
            VirtualPathData vpd = routeCollection.GetVirtualPathForArea(requestContext, routeName, mergedRouteValues);
            string modifiedUrl = PathHelpers.GenerateClientUrl(requestContext.HttpContext,vpd.VirtualPath);

看看这里我们就用到了VirtualPathData的VirtualPath属性了。

在FormExtensions中有一个BeginRouteForm方法，该方法的使用方式和BeginForm方法差不多，就跳过了。现在我们来看看ClientValidationEnabled 和UnobtrusiveJavaScriptEnabled默认为什么是true？这2个属性都是调用ScopeCache实例的对应属性，而获取ScopeCache时通过ScopeCache的Get方法来完成的。该Get方法代码很简单：

[csharp] view plaincopyprint?public static ScopeCache Get(IDictionary<object, object> scope, HttpContextBase httpContext) { 
              if (httpContext == null && System.Web.HttpContext.Current != null) { 
                  httpContext = new HttpContextWrapper(System.Web.HttpContext.Current); 
              } 
 
              ScopeCache result = null; 
              scope = scope ?? ScopeStorage.CurrentScope; 
 
              if (httpContext != null) { 
                  result = httpContext.Items[_cacheKey] as ScopeCache; 
              } 
 
              if (result == null || result._scope != scope) { 
                  result = new ScopeCache(scope); 
 
                  if (httpContext != null) { 
                      httpContext.Items[_cacheKey] = result; 
                  } 
              } 
 
              return result; 
          } 
      } 

  public static ScopeCache Get(IDictionary<object, object> scope, HttpContextBase httpContext) {
                if (httpContext == null && System.Web.HttpContext.Current != null) {
                    httpContext = new HttpContextWrapper(System.Web.HttpContext.Current);
                }

                ScopeCache result = null;
                scope = scope ?? ScopeStorage.CurrentScope;

                if (httpContext != null) {
                    result = httpContext.Items[_cacheKey] as ScopeCache;
                }

                if (result == null || result._scope != scope) {
                    result = new ScopeCache(scope);

                    if (httpContext != null) {
                        httpContext.Items[_cacheKey] = result;
                    }
                }

                return result;
            }
        }

而ScopeStorage的CurrentScope属性是又是怎么来的了？

        public static IScopeStorageProvider CurrentProvider {
            get {  return _stateStorageProvider ?? _defaultStorageProvider; }
            set {   _stateStorageProvider = value; }
        }
        public static IDictionary<object, object> CurrentScope {
            get {
                return CurrentProvider.CurrentScope;
            }
        }
默认来自于StaticScopeStorageProvider的CurrentScope，该属性默认返回的是一个没有成员的IDictionary<object, object>实例。那么这里的CurrentProvider 默认是个说明东西了，在System.Web.WebPages项目中的PreApplicationStartCode有这么一句  ScopeStorage.CurrentProvider = new AspNetRequestScopeStorageProvider(); 在AspNetRequestScopeStorageProvider的够着函数有这么一句ApplicationScope = new ApplicationScopeStorageDictionary(); 在ApplicationScopeStorageDictionary的构造函数中有    public ApplicationScopeStorageDictionary()  : this(new WebConfigScopeDictionary()) {   }，WebConfigScopeDictionary的够着函数又有    public WebConfigScopeDictionary()  :this(WebConfigurationManager.AppSettings) {  }这么一句，
不知道大家是否还记得在ControllerBase的Execute方法中有这么一句 using (ScopeStorage.CreateTransientScope()) { ExecuteCore(); }

public static IDisposable CreateTransientScope() {
return CreateTransientScope(new ScopeStorageDictionary(baseScope: CurrentScope));
}
  public static IDisposable CreateTransientScope(IDictionary<object, object> context) {
            var currentContext = CurrentScope;
            CurrentProvider.CurrentScope = context;
            return new DisposableAction(() => CurrentProvider.CurrentScope = currentContext); // Return an IDisposable that pops the item back off

        }

现在我们知道了IScopeStorageProvider 的CurrentProvider是什么东西了，是一个AspNetRequestScopeStorageProvider里面的数据实现从WebConfigurationManager.AppSettings这里取出来的。

 

我想大家现在该明白为什么这个ClientValidationEnabled 默认是true了吧。