组合框SelectedItem在源更改时不更新

我有一个viewmodel INotifyPropertyChanged . 在此viewModel上有一个名为 SubGroupingView . 此属性绑定到组合框的选定项。当我更改组合框时,源属性会被很好地更新,但是当我更改源属性或初始化控件时 combobox.selectedItem 不反映属性中存在的内容。

<ComboBox Grid.Column="3" Grid.Row="1" 
          Margin="0,1,4,1" 
          SelectedItem="{Binding Path=SubGroupingView, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay, diag:PresentationTraceSources.TraceLevel=High}" 
          ItemsSource="{Binding Columns}" 
          DisplayMemberPath="DisplayName">

物业提出 PropertyChanged 事件和TraceSource输出显示绑定检测到它并传输了值,只是combobox没有反映它。任何想法都欢迎!

编辑:
跟踪源的输出如下:

System.Windows.Data Warning: 91 : BindingExpression (hash=23631369): Got PropertyChanged event from ReportViewModel (hash=52844413)  
System.Windows.Data Warning: 97 : BindingExpression (hash=23631369): GetValue at level 0 from ReportViewModel (hash=52844413) using RuntimePropertyInfo(SubGroupingView):         DataColumnViewModel (hash=58231222)  
System.Windows.Data Warning: 76 : BindingExpression (hash=23631369): TransferValue - got raw value DataColumnViewModel (hash=58231222)  
System.Windows.Data Warning: 80 : BindingExpression (hash=23631369): TransferValue - implicit converter produced DataColumnViewModel (hash=58231222)  
System.Windows.Data Warning: 85 : BindingExpression (hash=23631369): TransferValue - using final value DataColumnViewModel (hash=58231222)  

public class ReportViewModel : ViewModelBase, IReportTemplate
{
    public DataColumnViewModel SubGroupingView
    {
        get
        {
            return GetViewModel(_report.SubGrouping);
        }
        set
        {
            if (_report.SubGrouping == value.ColumnName)
                return;
            _report.SubGrouping = value.ColumnName;
            RefreshDataSeries();
            base.OnPropertyChanged("SubGroupingView");
            base.OnPropertyChanged("IsReady");
        }

    }
}

注: ViewModelBase INotifyPropertyChange .

回答
GetHashCode() Equals(object) 现在它运行得很好。谢谢你的帮助!