在升级到MVC3RTM之后,我在以前工作的地方得到了一个异常。
这是一个场景。我有几个对象使用相同的底层接口IActivity和IOwned。
IActivity implements IOwned (another interface)
public interface IActivity:IOwned {...}
public interface IOwned
{
int? AuthorId {get;set;}
}
我有一个局部视图,它使用IActivity重用其他具体的部分。
下面是活动Partial的定义。
<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<IActivity>" %>
<%: Html.HiddenFor(item => item.AuthorId) %>
然而,它抛出了一个异常。它在ModelMetadata中找不到AuthorId。
我猜在以前的版本中,它查看了IActivity实现的接口。
有什么想法,建议,不是到处重复相似的界面吗?
已复制下面的堆栈跟踪。
[ArgumentException: The property IActivity.AuthorId could not be found.]
System.Web.Mvc.AssociatedMetadataProvider.GetMetadataForProperty(Func`1 modelAccessor, Type containerType, String propertyName) +498313
System.Web.Mvc.ModelMetadata.GetMetadataFromProvider(Func`1 modelAccessor, Type modelType, String propertyName, Type containerType) +101
System.Web.Mvc.ModelMetadata.FromLambdaExpression(Expression`1 expression, ViewDataDictionary`1 viewData) +393
System.Web.Mvc.Html.InputExtensions.HiddenFor(HtmlHelper`1 htmlHelper, Expression`1 expression, IDictionary`2 htmlAttributes) +57
System.Web.Mvc.Html.InputExtensions.HiddenFor(HtmlHelper`1 htmlHelper, Expression`1 expression) +51
ASP.views_shared_activity_ascx.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in c:\Users\...\Documents\Visual Studio 2010\Projects\ngen\trunk\...\Views\Shared\Activity.ascx:3
System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +109
System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +8
System.Web.UI.Control.Render(HtmlTextWriter writer) +10
System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +208
System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +8
System.Web.UI.Page.Render(HtmlTextWriter writer) +29
System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer) +43
System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3060
发布于 2011-10-20 03:21:57
感谢Burcephal,谁的回答给我指明了正确的方向?
你可以创建一个MetaDataProvider来解决这个问题,这里的代码添加到基类中的代码中,检查模型的已实现接口上的属性,而模型本身就是一个接口。
public class MyMetadataProvider
: EmptyModelMetadataProvider {
public override ModelMetadata GetMetadataForProperty(
Func<object> modelAccessor, Type containerType, string propertyName) {
if (containerType == null) {
throw new ArgumentNullException("containerType");
}
if (String.IsNullOrEmpty(propertyName)) {
throw new ArgumentException(
"The property '{0}' cannot be null or empty", "propertyName");
}
var property = GetTypeDescriptor(containerType)
.GetProperties().Find(propertyName, true);
if (property == null
&& containerType.IsInterface) {
property = (from t in containerType.GetInterfaces()
let p = GetTypeDescriptor(t).GetProperties()
.Find(propertyName, true)
where p != null
select p
).FirstOrDefault();
}
if (property == null) {
throw new ArgumentException(
String.Format(
CultureInfo.CurrentCulture,
"The property {0}.{1} could not be found",
containerType.FullName, propertyName));
}
return GetMetadataForProperty(modelAccessor, containerType, property);
}
}
如上所述,将提供程序设置为global.asax Application_Start
ModelMetadataProviders.Current = new MyMetaDataProvider();
发布于 2011-09-07 02:21:19
如果你感兴趣,我已经在我的应用程序中实现了一些工作。当我浏览MVC源代码时,我发现下面命名的FromLambdaExpression方法将调用MetaDataProvider,这是一个可覆盖的单例。所以我们可以只实现这个类,如果第一个接口不起作用,它将实际尝试继承的接口。它还将在接口树上向上移动。
public class MyMetaDataProvider : EmptyModelMetadataProvider
{
public override ModelMetadata GetMetadataForProperty(Func<object> modelAccessor, Type containerType, string propertyName)
{
try
{
return base.GetMetadataForProperty(modelAccessor, containerType, propertyName);
}
catch(Exception ex)
{
//Try to go up to type tree
var types = containerType.GetInterfaces();
foreach (var container in types)
{
if (container.GetProperty(propertyName) != null)
{
try
{
return GetMetadataForProperty(modelAccessor, container, propertyName);
}
catch
{
//This interface did not work
}
}
}
//If nothing works, then throw the exception
throw ex;
}
}
}
然后,只需更改global.asax Application_Start()中的MetaDataProvider实现。
ModelMetadataProviders.Current = new MyMetaDataProvider();
这不是最好的代码,但它可以完成这项工作。
发布于 2011-03-21 15:56:52
尝试使用类型转换。它适用于我的项目,尽管resharper强调它是多余的。
对于您的代码,解决方案是
<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<IActivity>" %>
<%: Html.HiddenFor(item => ((IOwned)item).AuthorId) %>
https://stackoverflow.com/questions/4702483
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