1

我想将每个组选择到自定义类中，将每个项目选择到另一个自定义类中，

我这样做是这样的：

_notificationsManager
    .GetUserNotifications(_repositoryNotifications, _memberShipProvider)
    .GroupBy(x => x.Category)
    .Select(g => new NotificationsGroupData {
          Name = g.Key,
          Notifications = g.Take(3).Select(s => new NotificationData  {
                                           Category = g.Key,
                                           Text = s.Text,
                                           Time = DateTime.Now.Subtract(s.Time)
                                         })
     })

这里是 NotificationsGroupData：

public class NotificationsGroupData
{
    public string Name { get; set; }
    public IEnumerable<NotificationData> Notifications { get; set; }
}

和通知数据：

public class NotificationData
{
    public virtual TimeSpan Time { get; set; }
    public virtual string Category { get; set; }
    public virtual string Text { get; set; }
}

但是当我试图创建循环时，我得到了错误：方法或操作没有实现。

在这条线上：

@foreach (var group in Model.Notifications)

我该如何解决？

Uodate： 我将代码更新为：

_notificationsManager.GetUserNotifications(_repositoryNotifications, _memberShipProvider)
                                             .GroupBy(x => x.Category)
                                             .Select(g => new
                                                 {
                                                     Name = g.Key,
                                                     Notifications =
                                                              g.OrderBy(o => o.Time)
                                                               .Take(3)
                                                               .Select(s => new
                                                                   {
                                                                       Category = g.Key,
                                                                       s.Text,
                                                                       s.Time
                                                                   })
                                                 }).AsEnumerable().Select(g => new NotificationsGroupData
                                                     {
                                                         Name = g.Name,
                                                         Notifications = g.Notifications
                                                                          .Select(s => new NotificationData
                                                                              {
                                                                                  Category = g.Name,
                                                                                  Text = s.Text,
                                                                                  Time = now - s.Time
                                                                              })
                                                     })

这里是错误：

The method or operation is not implemented.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.NotImplementedException: The method or operation is not implemented.

Source Error: @foreach (var group in Model.Notifications)

Stack Trace: 


[NotImplementedException: The method or operation is not implemented.] NHibernate.Linq.GroupBy.NonAggregatingGroupByRewriter.FlattenSubQuery(SubQueryExpression subQueryExpression, QueryModel queryModel) +608    NHibernate.Linq.GroupBy.NonAggregatingGroupByRewriter.ReWrite(QueryModel queryModel) +598    NHibernate.Linq.Visitors.QueryModelVisitor.GenerateHqlQuery(QueryModel queryModel, VisitorParameters parameters, Boolean root) +126    NHibernate.Linq.NhLinqExpression.Translate(ISessionFactoryImplementor sessionFactory) +208    NHibernate.Hql.Ast.ANTLR.ASTQueryTranslatorFactory.CreateQueryTranslators(String queryIdentifier, IQueryExpression queryExpression, String collectionRole, Boolean shallow, IDictionary`2 filters, ISessionFactoryImplementor factory) +51    NHibernate.Engine.Query.HQLExpressionQueryPlan.CreateTranslators(String expressionStr, IQueryExpression queryExpression, String collectionRole, Boolean shallow, IDictionary`2 enabledFilters, ISessionFactoryImplementor factory) +100    NHibernate.Engine.Query.HQLExpressionQueryPlan..ctor(String expressionStr, IQueryExpression queryExpression, String collectionRole, Boolean shallow, IDictionary`2 enabledFilters, ISessionFactoryImplementor factory) +74    NHibernate.Engine.Query.HQLExpressionQueryPlan..ctor(String expressionStr, IQueryExpression queryExpression, Boolean shallow, IDictionary`2 enabledFilters, ISessionFactoryImplementor factory) +53  NHibernate.Engine.Query.QueryPlanCache.GetHQLQueryPlan(IQueryExpression queryExpression, Boolean shallow, IDictionary`2 enabledFilters) +320   NHibernate.Impl.AbstractSessionImpl.GetHQLQueryPlan(IQueryExpression queryExpression, Boolean shallow) +188    NHibernate.Impl.AbstractSessionImpl.CreateQuery(IQueryExpression queryExpression) +164    NHibernate.Linq.DefaultQueryProvider.PrepareQuery(Expression expression, IQuery& query, NhLinqExpression& nhQuery) +152    NHibernate.Linq.DefaultQueryProvider.Execute(Expression expression)
+70    NHibernate.Linq.DefaultQueryProvider.Execute(Expression expression) +59    Remotion.Linq.QueryableBase`1.GetEnumerator() +128  System.Linq.WhereSelectEnumerableIterator`2.MoveNext() +61    ASP._Page_Views_Layout_Notifications_cshtml.Execute() in d:\Dev\Projects\ADDE\ADDE\Views\Layout\Notifications.cshtml:21    System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +197    System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +103    System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +88    System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +235    System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +107    System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
+291    System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +13    System.Web.Mvc.<>c__DisplayClass1a.<InvokeActionResultWithFilters>b__17()
+23    System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) +245   System.Web.Mvc.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19()
+22    System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) +176    System.Web.Mvc.Async.<>c__DisplayClass2a.<BeginInvokeAction>b__20()
+75    System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__22(IAsyncResult asyncResult) +99    System.Web.Mvc.Async.WrappedAsyncResult`1.End()
+50    System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +27    System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult) +14    System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +23    System.Web.Mvc.Async.WrappedAsyncResult`1.End() +55    System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +39 System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +23    System.Web.Mvc.Async.WrappedAsyncResult`1.End() +55    System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +29    System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10    System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult) +25    System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +23    System.Web.Mvc.Async.WrappedAsyncResult`1.End() +55    System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult)
+31    System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9    System.Web.Mvc.<>c__DisplayClassa.<EndProcessRequest>b__9() +22    System.Web.Mvc.<>c__DisplayClass4.<Wrap>b__3() +10    System.Web.Mvc.ServerExecuteHttpHandlerWrapper.Wrap(Func`1 func) +27   System.Web.Mvc.ServerExecuteHttpHandlerWrapper.Wrap(Action action) +64 System.Web.Mvc.ServerExecuteHttpHandlerAsyncWrapper.EndProcessRequest(IAsyncResult result) +71    System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride) +1464

[HttpException (0x80004005): Error executing child request for handler 'System.Web.Mvc.HttpHandlerUtil+ServerExecuteHttpHandlerAsyncWrapper'.] System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride) +3033503    System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage) +76    System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) +28    System.Web.HttpServerUtilityWrapper.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) +19    System.Web.Mvc.Html.ChildActionExtensions.ActionHelper(HtmlHelper htmlHelper, String actionName, String controllerName, RouteValueDictionary routeValues, TextWriter textWriter) +463    System.Web.Mvc.Html.ChildActionExtensions.RenderAction(HtmlHelper htmlHelper, String actionName, String controllerName) +35    ASP._Page_Views_Shared__Layout_cshtml.Execute() in d:\Dev\Projects\ADDE\ADDE\Views\Shared\_Layout.cshtml:33    System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +197    System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +103    System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +88    System.Web.WebPages.<>c__DisplayClass7.<RenderPageCore>b__6(TextWriter writer) +233    System.Web.WebPages.HelperResult.WriteTo(TextWriter writer) +10    System.Web.WebPages.WebPageBase.Write(HelperResult result) +71    System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action`1 body) +64    System.Web.WebPages.WebPageBase.PopContext() +246    System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +95    System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +235    System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +107    System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
+291    System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +13    System.Web.Mvc.<>c__DisplayClass1a.<InvokeActionResultWithFilters>b__17()
+23    System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) +245   System.Web.Mvc.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19()
+22    System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) +176    System.Web.Mvc.Async.<>c__DisplayClass2a.<BeginInvokeAction>b__20()
+75    System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__22(IAsyncResult asyncResult) +99    System.Web.Mvc.Async.WrappedAsyncResult`1.End()
+50    System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +27    System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult) +14    System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +23    System.Web.Mvc.Async.WrappedAsyncResult`1.End() +55    System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +39 System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +23    System.Web.Mvc.Async.WrappedAsyncResult`1.End() +55    System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +29    System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10    System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult) +25    System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +23    System.Web.Mvc.Async.WrappedAsyncResult`1.End() +55    System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult)
+31    System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9    System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
+9629708    System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155
4

2 回答 2

1

我怀疑问题很可能出在DateTime.Now.Subtract(s.Time)其中，可能与您对NotificationsGroupData.

我建议您将查询更改为简单地获取您需要的所有数据而不进行太多处理，然后在本地使用AsEnumerable. 所以像：

// Use a single common idea of "now", don't re-evaluate each time
var now = DateTime.Now;
var query = _notificationsManager
    .GetUserNotifications(_repositoryNotifications, _memberShipProvider)
    .GroupBy(x => x.Category)
    .Select(g => new {
      Name = g.Key,
      Notifications = g.Take(3)
                       .Select(s => new {
                           Text = s.Text,
                           Time = s.Time
                       })
    })
    .AsEnumerable() // Force local evaluation for final step
    .Select(g => new NotificationsGroupData {
      Name = g.Name,
      Notifications = g.Notifications
                       .Select(s => new NotificationData {
                           Category = g.Name,
                           Text = s.Text,
                           Time = now - s.Time
                       })
    });

编辑：好的，因为这仍然存在问题，您可以尝试在进程中进行分组后的所有操作：

var now = DateTime.Now;
var query = _notificationsManager
    .GetUserNotifications(_repositoryNotifications, _memberShipProvider)
    .GroupBy(x => x.Category)
    .AsEnumerable() // Force local evaluation for final step
    .Select(g => new NotificationsGroupData {
      Name = g.Key,
      Notifications = g.Take(3)
                       .Select(s => new NotificationData {
                           Category = g.Key,
                           Text = s.Text,
                           Time = now - s.Time
                       })
    });

请注意，这远非想法 - 它会从数据库中提取所有属性，而不仅仅是您想要的属性。（不仅是前三个——虽然“第一个”也取决于顺序，但在我们可以看到的任何地方都没有指定。）这可能是您需要回退到 SQL 的情况之一，但听起来 NHibernate 可以为你做更多的事情......

于 2013-04-06T07:06:10.180 回答
1

NHibernate 无法将您的查询转换为 sql。最快的解决方案是在内存集合上做出选择声明，而不是将其传递给 NHibernate。试试这个： 

_notificationsManager
    .GetUserNotifications(_repositoryNotifications, _memberShipProvider)
    .GroupBy(x => x.Category)
    .ToList()
    .Select(g => new NotificationsGroupData {
          Name = g.Key,
          Notifications = g.Take(3).Select(s => new NotificationData  {
                                           Category = g.Key,
                                           Text = s.Text,
                                           Time = DateTime.Now.Subtract(s.Time)
                                         })
     })

另一个选择是在 HQL\SQL 上编写您的查询并将其传递给 NHibernate，因此您将从数据库中提取必要数量的数据，然后将其映射到您的自定义实体。

于 2013-04-06T08:08:18.470 回答