[英]Get the parent object from child in entity framework without a foreign key
我負責視圖/視圖模型,而不是項目的模型。 模型設置如下:
[Table("Activity")]
public class Activity
{
[Key]
public int ActivityId { get; set; }
public string OtherProperties { get; set; }
}
[Table("Class1")]
public class Class1
{
[Key]
public int Class1Id { get; set; }
public string Name { get; set; }
public ObservableCollection<Activity> Activities { get; set; }
}
[Table("Class2")]
public class Class2
{
[Key]
public int Class2Id { get; set; }
public string Name { get; set; }
public ObservableCollection<Activity> Activities { get; set; }
}
編輯
我試圖通過對Activity類進行調用來填充DataGrid。 該網格在另一類中具有“名稱”屬性的列。 如何通過ViewModel從Activity類的兩個類中獲取“名稱”列的列表(或Class對象本身的列表)?
WPF
<DataGrid ItemsSource="{Binding Activities}"
Grid.ColumnSpan="3"
Grid.Row="1"
HorizontalAlignment="Stretch"
AutoGenerateColumns="False"
>
<DataGrid.Columns>
<DataGridTemplateColumn Header="Complete">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<Button Command="{Binding Path=DataContext.CompleteTaskCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:BasePage}}}"
CommandParameter="{Binding ActivityId}"
Content="{StaticResource FontAwesomeCheckIcon}"
Foreground="Green"
Grid.Column="0"
HorizontalAlignment="Center"
Style="{StaticResource FontAwesomeIconButton}"
VerticalAlignment="Center"
/>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
<DataGridTextColumn Binding="{Binding DueDate, StringFormat=MM/dd/yyyy, Converter={local:UtcToLocalDateTimeValueConverter}}" Header="Due Date"/>
<DataGridTextColumn Binding="{Binding IsComplete, Converter={local:BooleanToStringParameterValueConverter}, ConverterParameter=CompletedOpen}" Header="Status"/>
<DataGridTextColumn Binding="{Binding Subject}" Header="Subject"/>
<DataGridTextColumn Binding="{Binding Name}" Header="Name"/> ??????????
</DataGrid.Columns>
</DataGrid>
視圖模型
Activities= DB.GetAll<Activity>().Where(x => x.IsDeleted == false && x.AssignedTo == user);
GetAll方法
public IEnumerable<T> GetAll<T>() where T : EcoDevBase, new()
{
// if no items, returns an empty list
IEnumerable<T> entityList = _Context.Set<T>().ToList();
return entityList;
}
我不確定您一開始的設置是什么,但是可以使用LINQ通過多種方法來滿足您的要求。 例如:
var desiredActivity = Activity;
var class1Names = DbContext.Class1.Where(e => e.Activities.Contains(desiredActivity).Select(e => e.Name)
var class2Names = DbContext.Class2.Where(e => e.Activities.Contains(desiredActivity).Select(e => e.Name)
var listOfNames = new List<string>;
listOfNames.AddRange(class1Names);
listOfNames.AddRange(class2Names);
它可能不是最理想的解決方案,但是您沒有提供太多有關您要如何處理業務對象的信息。
編輯:
參照ViewModel,您具有所需活動的列表,現在您想知道哪個Class對象包含此活動,那么您可以執行以下操作:
var listOfNames = new List<string>;
foreach (var activity in Activities)
{
var class1Names = DbContext.Class1.Where(e => e.Activities.Contains(activity).Select(e => e.Name)
var class2Names = DbContext.Class2.Where(e => e.Activities.Contains(activity).Select(e => e.Name)
listOfNames.AddRange(class1Names);
listOfNames.AddRange(class2Names);
}
現在,您可以通過調用以下方法從listOfNames中刪除重復項:
var fixedListOfNames = new List<string>;
fixedListOfNames.AddRange(listOfNames.Distinct());
如果要獲取對象列表,則可以執行以下操作:
var listOfClasses1 = new List<Class1>;
var listOfClasses2 = new List<Class2>;
foreach (var activity in Activities)
{
var class1Names = DbContext.Class1.Where(e => e.Activities.Contains(activity);
var class2Names = DbContext.Class2.Where(e => e.Activities.Contains(activity);
listOfClasses1.AddRange(class1Names);
listOfClasses2.AddRange(class2Names);
}
我不確定您的配置,但您可能還需要添加
using System.Data.Entity
和/或.Include(e => e.Activities)
到您的查詢中。
最后,如果您是我,我將創建一個業務對象類,其中包含DataGrid所需的屬性,這些屬性不適用於db對象。
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