Question

我有以下EF对象列表Leagues，其中每个对象都有一个Teams列表。每个Team都有一个与之关联的年份

在WPF表单中，我有combobox可以选择多年。当我选择一年时，我希望能够按该年存在的联赛进行排序，再按其拥有的球队进行排序，以便可以为此填充TreeView。

到目前为止，我得到的最多是：

    public int SelectedYear
    {
        get => _SelectedYear;
        set
        {
            _SelectedYear = value;
            RaisePropertyChangedEvent("SelectedYear");
            Refresh();
        }
    }

    public void Refresh(object sender = null, EventArgs e = null)
    {
        Leagues = new ObservableCollection<League>(_Locator.Statistix.Leagues.Where(x => x.Teams.Count(t => t.Year == SelectedYear) > 0).ToList());
        foreach(League l in Leagues)
        {
            l.Teams.Where(x => x.Year == SelectedYear);
        }
    }

League对象如下：

public partial class League
{
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
    public League()
    {
        this.Teams = new HashSet<Team>();
    }

    public int ID { get; set; }
    public string Name { get; set; }
    public string Initials { get; set; }
    public string LahmanID { get; set; }

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<Team> Teams { get; set; }
}

出于良好的考虑，这里也是Team对象：

public partial class Team
{
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
    public Team()
    {
        this.Games = new HashSet<Game>();
        this.Games1 = new HashSet<Game>();
    }

    public int ID { get; set; }
    public int FranchiseID { get; set; }
    public int Year { get; set; }
    public Nullable<int> CityID { get; set; }
    public string Nickname { get; set; }
    public Nullable<int> BallparkID { get; set; }
    public int LeagueID { get; set; }

    public virtual City City { get; set; }
    public virtual Franchise Franchise { get; set; }
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<Game> Games { get; set; }
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<Game> Games1 { get; set; }
    public virtual League League { get; set; }
}

有没有一种方法可以过滤同一个Leagues ObservableCollection内的联赛及其后的联赛？

Answer 1

如果联赛的规模不是太大，我会考虑收集数据，然后提取不需要的数据。

!ENTRY org.eclipse.osgi 4 0 2018-09-23 00:28:48.688
!MESSAGE Application error
!STACK 1
org.eclipse.e4.core.di.InjectionException: java.lang.NoClassDefFoundError: javax/annotation/PostConstruct
    at org.eclipse.e4.core.internal.di.InjectorImpl.internalMake(InjectorImpl.java:410)
    at org.eclipse.e4.core.internal.di.InjectorImpl.make(InjectorImpl.java:318)
    at org.eclipse.e4.core.contexts.ContextInjectionFactory.make(ContextInjectionFactory.java:162)
    at org.eclipse.e4.ui.internal.workbench.swt.E4Application.createDefaultHeadlessContext(E4Application.java:491)
    at org.eclipse.e4.ui.internal.workbench.swt.E4Application.createDefaultContext(E4Application.java:505)
    at org.eclipse.e4.ui.internal.workbench.swt.E4Application.createE4Workbench(E4Application.java:204)
    at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:614)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:594)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:148)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:151)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:388)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:243)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:653)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:590)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1499)
Caused by: java.lang.NoClassDefFoundError: javax/annotation/PostConstruct
    at org.eclipse.e4.core.internal.di.InjectorImpl.inject(InjectorImpl.java:124)
    at org.eclipse.e4.core.internal.di.InjectorImpl.internalMake(InjectorImpl.java:399)
    ... 22 more
Caused by: java.lang.ClassNotFoundException: javax.annotation.PostConstruct cannot be found by org.eclipse.e4.core.di_1.6.100.v20170421-1418
        at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:433)
        at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:395)
        at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:387)
        at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:150)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)
        ... 24 more

!ENTRY org.eclipse.e4.ui.workbench 4 0 2018-09-23 00:28:48.695
!MESSAGE FrameworkEvent ERROR
!STACK 0
java.lang.NoClassDefFoundError: javax/annotation/PreDestroy
        at org.eclipse.e4.core.internal.di.InjectorImpl.disposed(InjectorImpl.java:450)
        at org.eclipse.e4.core.internal.di.Requestor.disposed(Requestor.java:156)
        at org.eclipse.e4.core.internal.contexts.ContextObjectSupplier$ContextInjectionListener.update(ContextObjectSupplier.java:78)
        at org.eclipse.e4.core.internal.contexts.TrackableComputationExt.update(TrackableComputationExt.java:111)
        at org.eclipse.e4.core.internal.contexts.TrackableComputationExt.handleInvalid(TrackableComputationExt.java:74)
        at org.eclipse.e4.core.internal.contexts.EclipseContext.dispose(EclipseContext.java:178)
        at org.eclipse.e4.core.internal.contexts.osgi.EclipseContextOSGi.dispose(EclipseContextOSGi.java:99)
        at org.eclipse.e4.core.internal.contexts.osgi.EclipseContextOSGi.bundleChanged(EclipseContextOSGi.java:141)
        at org.eclipse.osgi.internal.framework.BundleContextImpl.dispatchEvent(BundleContextImpl.java:908)
        at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
        at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:148)
        at org.eclipse.osgi.internal.framework.EquinoxEventPublisher.publishBundleEventPrivileged(EquinoxEventPublisher.java:213)
        at org.eclipse.osgi.internal.framework.EquinoxEventPublisher.publishBundleEvent(EquinoxEventPublisher.java:120)
        at org.eclipse.osgi.internal.framework.EquinoxEventPublisher.publishBundleEvent(EquinoxEventPublisher.java:112)
        at org.eclipse.osgi.internal.framework.EquinoxContainerAdaptor.publishModuleEvent(EquinoxContainerAdaptor.java:168)
        at org.eclipse.osgi.container.Module.publishEvent(Module.java:476)
        at org.eclipse.osgi.container.Module.doStop(Module.java:634)
        at org.eclipse.osgi.container.Module.stop(Module.java:498)
        at org.eclipse.osgi.container.SystemModule.stop(SystemModule.java:202)
        at org.eclipse.osgi.internal.framework.EquinoxBundle$SystemBundle$EquinoxSystemModule$1.run(EquinoxBundle.java:165)
        at java.base/java.lang.Thread.run(Thread.java:844)
Caused by: java.lang.ClassNotFoundException: javax.annotation.PreDestroy cannot be found by org.eclipse.e4.core.di_1.6.100.v20170421-1418
        at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:433)
        at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:395)
        at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:387)
        at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:150)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)

另一种选择是构建ObserableCollection固有的特殊类并实现IObseravable，以便构建特殊逻辑以将这些类用作WPF表单的数据上下文，这将允许系统在选择不同年份时自动进行过滤

Answer 2

要将多个列表拼合为一个列表，可以使用SelectMany：

// all teams from all leagues
var allTeams = GetAllLeagues().SelectMany(l => l.Teams);

// all teams of the SelectedYear
var teamsByYear = allTeams.Where(t => t.Year == SelectedYear);

Answer 3

public void Refresh(object sender = null, EventArgs e = null)
{
    Leagues = _Locator.Statistix.Leagues.Select(x => new League
        {
             Id = x.Id,
             Name = x.Name,
             Initials = x.Initials,
             LahmanId = x.LahmanId,
             Teams = x.Teams.Where(x => x.Year == SelectedYear).ToList()
        }).Where(x=> x.Teams.Count > 0).ToList();
}

列表中的LINQ查询列表

3 个答案: