WPF：树视图不从数据库

Question

我有一个包含此字段的表（id，ParentId，title，...），其名称为HesabCoding。

我想将此表绑定到带有SQL过程的TreeView，即GetAll表行。

型号：

public class HesabCoding : NotifyPropertyChangedHelper, IDataErrorInfo
{
    private int id;
    private string title;
    private string fullTitle;
    private string hesabCode;
    private string fullHesabCode;
    private short hesabGroup_FK;
    private string hesabGroup;
    private int parentId;
    public ObservableCollection<HesabCoding> HesabCodings { get; set; }

    public HesabCoding()
    {
        HesabCodings = new ObservableCollection<HesabCoding>();
    }

在HesabCoding VM中：

private ObservableCollection<HesabCoding> _HesabCodingCollection;
    public ObservableCollection<HesabCoding> HesabCodingCollection
    {
        get { return this._HesabCodingCollection; }
        set
        {
            this._HesabCodingCollection = value;
            base.OnPropertyChanged("HesabCodingCollection");
        }
    }
public void HesabCodingSelect()
    {
        string _errorMessage = "";
        int tmpSelectedIndex = SelectedIndex;
        ObservableCollection<HesabCoding> _HesabCodingModelCollection = new ObservableCollection<HesabCoding>();
        _HesabCodingModelCollection = HesabCodingDAL.HesabCodingSelect(false, out _errorMessage);
    }

在Xaml中

：

<TreeView  Name="TrHesabCoding" Grid.Row="1" ItemsSource="{Binding HesabCodingCollection}">
        <TreeView.ItemContainerStyle>
            <Style TargetType="{x:Type TreeViewItem}">
                <Setter Property="IsExpanded" Value="True"/>
            </Style>
        </TreeView.ItemContainerStyle>
        <TreeView.ItemTemplate>
            <HierarchicalDataTemplate ItemsSource="{Binding HesabCodings}" DataType="{x:Type myCustomData:HesabCoding}" >
                <TextBlock Text="{Binding Title}" />
            </HierarchicalDataTemplate>
        </TreeView.ItemTemplate>
    </TreeView>

我在SQL中的过程：

SELECT  
    hc.id, hc.HesabCode, hc.Title, hc.HesabStructure_FK,
    hs2.Title AS HesabStructure,
    hc.HesabEntity_FK, he.Title AS HesabEntity, 
    hc.HesabGroup_FK, hg.Title AS HesabGroup,
    ISNULL(hc.ParentId, 0) ParentId,
WHERE  
    (hc.ParentId = @HesabCodingId OR 
     (@HesabCodingId IS NULL AND hc.ParentId IS NULL))

DAL班级：

public ObservableCollection<HesabCoding> HesabCodingSelect(bool onlyActive,out string errorMessage)
    {
        using (var dbcontext = new AccountingDataContext(AppData.userDbConnectionString))
        {
            try
            {
                errorMessage = null;

                var Ret = dbcontext.HesabCodingSelect(onlyActive);

                List<HesabCoding> hesabCodingModelList = new List<HesabCoding>();

                CastObjectHelper.CastObjectResultToList(Ret, ref hesabCodingModelList);

                ObservableCollection<HesabCoding> hesabCodingModelCollection = new ObservableCollection<HesabCoding>(hesabCodingModelList);

                return hesabCodingModelCollection;
            }

            catch (Exception ex)
            {
                errorMessage = ex.Message;
                return null;
            }
        }
    }

如果parentid为Null则为root。

我的问题是我的树视图没有填充级联并填充级别1。