添加到集合中時出現「元素已經是另一個元素的子元素」錯誤

Question

我也有Datapager的Datagrid/Dataform設置。我的DataPager.PageSize被聲明性地設置爲10.所有三個控件的My ItemsSource都設置爲QueryableCollectionView。如果我的收藏少於10條記錄，那麼向集合中添加新項目並沒有任何問題。我點擊我的DataForm（新項目）中的+號，填寫表單，捕獲DP上的edit_ended事件，並保存到我的SQL DB中，沒有問題。但是，當我有10多個項目，並且我單擊+符號（新項目）時，該應用程序會拋出「元素已經是另一個元素的子元素」錯誤。我不確定哪兩個控件（Gridview或DataPager）導致這個問題，我也不知道如何解決它！

碼（XAML）：

<toolkit:DataForm x:Name="dataForm" 
    Width="{Binding Width, ElementName=GV1}" 
    CurrentItem="{Binding SelectedWOEquipment}" 
    ItemsSource="{Binding WOEquipmentItems}" 
    AutoEdit="False" 
    Tag="Equipment" 
Header="Add/Update Equipment" 
    AutoCommit="False" 
    Margin="0,0,0,10" > 
    <i:Interaction.Triggers> 
     <i:EventTrigger EventName="EditEnded"> 
      <cmd:EventToCommand Command="{Binding SaveEquipmentCommand}" PassEventArgsToCommand="True"/> 
     </i:EventTrigger> 
     <i:EventTrigger EventName="DeletingItem"> 
      <cmd:EventToCommand Command="{Binding DeleteCommand}" 
       CommandParameter="{Binding Tag, ElementName=dataForm}"/> 
     </i:EventTrigger> 
    </i:Interaction.Triggers> 
    <toolkit:DataForm.ReadOnlyTemplate> 
     <DataTemplate> 
      <StackPanel> 
       <toolkit:DataField> 
        <TextBox Text="{Binding EquipmentCode}" /> 
       </toolkit:DataField> 
       <toolkit:DataField Label="Equipment Description"> 
        <TextBox Text="{Binding EquipmentDescription}" /> 
       </toolkit:DataField> 
       <toolkit:DataField Label="Hours"> 
        <TextBox IsEnabled="False" Text="{Binding Hours}" /> 
       </toolkit:DataField> 
      </StackPanel> 
     </DataTemplate> 
    </toolkit:DataForm.ReadOnlyTemplate> 
    <toolkit:DataForm.EditTemplate> 
     <DataTemplate> 
      <StackPanel> 
       <toolkit:DataField Label="Equipment Codes"> 
        <TextBox Text="{Binding EquipmentCode}" /> 
       </toolkit:DataField> 
       <toolkit:DataField Label="Equipment Description"> 
        <TextBox IsEnabled="False" 
      Text="{Binding EquipmentDescription}" /> 
       </toolkit:DataField> 
       <toolkit:DataField Label="Hours"> 
        <TextBox Text="{Binding Hours, Mode=TwoWay}" /> 
       </toolkit:DataField> 
      </StackPanel> 
     </DataTemplate> 
    </toolkit:DataForm.EditTemplate> 
    <toolkit:DataForm.NewItemTemplate> 
     <DataTemplate> 
      <StackPanel> 
       <toolkit:DataField Label="Equipment Codes"> 
        <telerik:RadComboBox x:Name="cboEquipment" 
      ItemsSource="{Binding DataSource.EquipmentList, Source={StaticResource DataContextProxy}}" 
         SelectedValue="{Binding EquipmentCode, Mode=TwoWay}" 
         Margin="0 0 20 0">          
         <telerik:RadComboBox.ItemsPanel> 
          <ItemsPanelTemplate> 
           <VirtualizingStackPanel/> 
          </ItemsPanelTemplate> 
         </telerik:RadComboBox.ItemsPanel> 
        </telerik:RadComboBox> 
       </toolkit:DataField> 
       <toolkit:DataField Visibility="Collapsed"> 
        <TextBox Text="{Binding EquipmentDescription,Mode=TwoWay}" /> 
       </toolkit:DataField> 
       <toolkit:DataField Label="Hours"> 
        <TextBox Text="{Binding Hours,Mode=TwoWay}" /> 
       </toolkit:DataField> 
      </StackPanel> 
     </DataTemplate> 
    </toolkit:DataForm.NewItemTemplate> 
</toolkit:DataForm> 
<Grid> 
    <Grid.RowDefinitions> 
     <RowDefinition Height="Auto" /> 
     <RowDefinition Height="*" /> 
    </Grid.RowDefinitions> 
    <telerik:RadGridView ItemsSource="{Binding WOEquipmentItems}" 
     x:Name="GV1" 
     ShowGroupPanel="False" 
     DataLoadMode="Asynchronous" 
     HorizontalAlignment="Left" 
     HeaderRowStyle="{StaticResource CSAgvHeaderRowStyle}" 
     SelectedItem="{Binding SelectedWOEquipment, Mode=TwoWay}" 
     AutoGenerateColumns="False" 
     IsReadOnly="True"> 
      <telerik:RadGridView.Columns> 
       <telerik:GridViewDataColumn DataMemberBinding="{Binding EquipmentCode}" HeaderCellStyle="{StaticResource CSAgvHeaderCellStyle}" Header="Equipment ID" Width="100"/> 
       <telerik:GridViewDataColumn DataMemberBinding="{Binding EquipmentDescription}" HeaderCellStyle="{StaticResource CSAgvHeaderCellStyle}" Header="Description" Width="300"/> 
       <telerik:GridViewDataColumn DataMemberBinding="{Binding Hours}" HeaderCellStyle="{StaticResource CSAgvHeaderCellStyle}" Header="Hours" Width="75"/> 
      </telerik:RadGridView.Columns> 
      <i:Interaction.Triggers> 
       <i:EventTrigger EventName="SelectedCellsChanged"> 
        <cmd:EventToCommand Command="{Binding EditEquipmentCommand}"/> 
       </i:EventTrigger> 
       </i:Interaction.Triggers> 
      </telerik:RadGridView> 
      <sdk:DataPager Grid.Row="1" Source="{Binding WOEquipmentItems}" PageSize="10" /> 

代碼（視圖模型） - WOEquipmentItems通過Web服務正確填充：

private QueryableCollectionView _WOEquipmentItems; 
private TSMVVM.Model.WOEquipment _selectedWOEquipment = new TSMVVM.Model.WOEquipment(); 
public QueryableCollectionView WOEquipmentItems 
    { 
     get { return _WOEquipmentItems; } 
     set 
     { 
      _WOEquipmentItems = value; 
      RaisePropertyChanged("WOEquipmentItems"); 
     } 
    } 
public TSMVVM.Model.WOEquipment SelectedWOEquipment 
    { 
     get 
     { 
      if (_selectedWOEquipment != null) 
      { 
       if (_selectedWOEquipment.EquipmentDescription == null && _selectedWOEquipment.EquipmentCode != null) 
       { 
        _selectedWOEquipment.EquipmentDescription = ""; 
        _selectedWOEquipment.EquipmentDescription = EquipmentDescriptionList[EquipmentList.IndexOf(_selectedWOEquipment.EquipmentCode)]; 
       } 
      } 
      return _selectedWOEquipment; 
     } 
     set 
     { 
      _selectedWOEquipment = value; 
      RaisePropertyChanged("SelectedWOEquipment"); 
     } 
    } 

Answer 1

解決方案竟然是可笑的簡單。我添加了這個：在我的ViewModel中，我註冊了這個命令，發射了一個簡單執行MyQuerableCollection.MoveToLastPage()的「AddingNewItem」函數。這迫使我的網格&尋呼機移動到最後一頁，這意味着我選擇的項目是可見的&不會引發錯誤。

編輯添加 - 當我的收藏精確到10時，它也拋出一個錯誤。所以我包括一個檢查，看看ItemCount％10 == 0.如果是這樣，我刪除列表中的第一個項目（Equipment.RemoveAt [0]）。因爲在設置新項目後，我運行LoadData（）函數，這不是問題。