【发布时间】：2013-05-15 22:10:16
【问题描述】：
我有实体，默认从引用自身的数据库表构建
我是新来的，声誉低，我不能添加图片，所以我会写我能写的。
区域：实体对象
属性：
身份证
ParentArea_ID
导航属性：
Areas - 区域集合
ParentArea - 实例化区域
我想用数据库表中的数据填充树视图。我找到了 2 个选项：使用来自 here 的包装器或绑定转换器。我是初学者，可能是错的，但使用 Binding Converter 对我来说是更好的方法。
我发现我必须使用 Areas 集合创建一个新类，以便更轻松地实现导航、添加、删除
class AreasCollection:ObservableCollection<Area>
{
private DBEntities _context;
public DBEntities Context
{
get { return _context; }
}
public AreasCollection(IEnumerable<Area> Areas, DBEntities context)
: base(Areas)
{
_context = context;
foreach (Area a in Areas)
{
a.Areas.AssociationChanged +=new CollectionChangeEventHandler(Areas_AssociationChanged);
}
}
void Areas_AssociationChanged(object sender, CollectionChangeEventArgs e)
{
if (e.Action == CollectionChangeAction.Remove)
{
this.Context.DeleteObject((Area)e.Element);
this.Context.DeleteObject((SpareDevice)e.Element);
this.Context.DeleteObject((AreaDevice)e.Element);
this.Context.DeleteObject((Executor)e.Element);
}
}
protected override void InsertItem(int index, Area item)
{
item.Areas.AssociationChanged += new CollectionChangeEventHandler(Areas_AssociationChanged);
this.Context.AddToAreas(item);
base.InsertItem(index, item);
}
protected override void RemoveItem(int index)
{
Area a = this[index];
a.Areas.AssociationChanged -= Areas_AssociationChanged;
for (int i = a.Areas.Count - 1; i >= 0; i--)
{
this.Context.DeleteObject(a.Areas.ElementAt(i));
}
for (int i = a.SpareDevices.Count - 1; i >= 0; i--)
{
this.Context.DeleteObject(a.SpareDevices.ElementAt(i));
}
for (int i = a.AreaDevices.Count - 1; i >= 0; i--)
{
this.Context.DeleteObject(a.AreaDevices.ElementAt(i));
}
for (int i = a.Executors.Count - 1; i >= 0; i--)
{
this.Context.DeleteObject(a.Executors.ElementAt(i));
}
this.Context.DeleteObject(this[index]);
base.RemoveItem(index);
}
}
我发现我必须做一个新的转换器类
public class AreasConverter : IValueConverter
{
public object Convert(object value, System.Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
var item = value as Area;
return item.Areas.Where(a => a.ParentArea_ID == item.ID);
}
public object ConvertBack(object value, System.Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
我的 XAML：
<TreeView Name="AreasTreeView" Height="350" ItemsSource="{Binding Converter={StaticResource AreasConverter}}" ItemTemplate="{StaticResource ItemTemplate}">
<TreeView.Resources>
<local:AreasConverter x:Key="AreasConverter"/>
<HierarchicalDataTemplate x:Key="ItemTemplate" ItemsSource="{Binding Converter={StaticResource AreasConverter}}">
<TextBlock Text="{Binding Path=ShortName}" />
</HierarchicalDataTemplate>
</TreeView.Resources>
</TreeView>
还有 XAML.cs
public partial class MainWindow : Window
{
private DBEntities context = new DBEntities();
private CollectionViewSource AreasConverterViewSourse;
private ListCollectionView AreasConverter;
public MainWindow()
{
InitializeComponent();
AreasTreeView.ItemsSource = context.Areas.Where(a => a.ParentArea_ID == null);
AreasConverterViewSourse = (CollectionViewSource)FindResource("AreasConverter");
this.AreasConverter = (ListCollectionView)this.AreasConverterViewSourse.View;
}
}
我有一个错误资源“ItemTemplate”无法解析。
如果我删除 ItemTemplate="{StaticResource ItemTemplate}"
来自
<TreeView Name="AreasTreeView" Height="350" ItemsSource="{Binding Converter={StaticResource AreasConverter}}" ItemTemplate="{StaticResource ItemTemplate}">
错误消失了，但是当我尝试运行应用程序时出现异常
System.Windows.Markup.XamlParseException occurred
HResult=-2146233087
Message='Provide value on 'System.Windows.StaticResourceExtension' threw an exception.' Line number '30' and line position '61'.
Source=PresentationFramework
LineNumber=30
LinePosition=61
StackTrace:
at System.Windows.Markup.WpfXamlLoader.Load(XamlReader xamlReader, IXamlObjectWriterFactory writerFactory, Boolean skipJournaledProperties, Object rootObject, XamlObjectWriterSettings settings, Uri baseUri)
at System.Windows.Markup.WpfXamlLoader.LoadBaml(XamlReader xamlReader, Boolean skipJournaledProperties, Object rootObject, XamlAccessLevel accessLevel, Uri baseUri)
at System.Windows.Markup.XamlReader.LoadBaml(Stream stream, ParserContext parserContext, Object parent, Boolean closeStream)
at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator)
at Maintenance.MainWindow.InitializeComponent() in c:\DATA\Maintenance\Maintenance\MainWindow.xaml:line 1
at Maintenance.MainWindow..ctor() in c:\DATA\Maintenance\Maintenance\MainWindow.xaml.cs:line 44
InnerException:
HResult=-2146233088
Message=Cannot find resource named 'AreasConverter'. Resource names are case sensitive.
Source=PresentationFramework
StackTrace:
at System.Windows.StaticResourceExtension.ProvideValue(IServiceProvider serviceProvider)
at MS.Internal.Xaml.Runtime.ClrObjectRuntime.CallProvideValue(MarkupExtension me, IServiceProvider serviceProvider)
InnerException:
这是我的第一个 wpf 应用程序和第一个数据库设计（16 个表）。从入门 sql server 和 wpf 视频开始，我已经为这个项目花费了 6 个弱点，谷歌搜索了几个小时和天。我的大脑开始沸腾。如果答案尽可能详细，我很乐意。
感谢您的帮助！
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标签： wpf binding treeview entity self-reference