wpf如何更新可观察集合中枚举属性更改的绑定？

Question

I have a class called SignalViewModel that implements INotifyPropertyChanged, and I am binding to the property in my xaml in the class SignalGraph, but the change is not propagating. The CLR property that I am trying to bind to is called BaseNotation. It is an enum defined as follows:

  public enum BaseNotation
  {
    Hex,
    SignedDecimal,
    UnsignedDecimal,
    SignaedBinary,
    UnsignedBinary
  }

the class and relevant source property

class SignalViewModel : INotifyPropertyChanged
{
    private BaseNotation _BaseRepresentation = BaseNotation.Hex;
        public BaseNotation BaseRepresentation
        {
          get
          {
            return _BaseRepresentation;
          }
          set
          {
            if (value != _BaseRepresentation)
            {
              _BaseRepresentation = (BaseNotation)value;
              OnPropertyChanged("BaseRepresentation");
            }
          }
        }

the target property is:

 public BaseNotation BaseRepresentation
    {
      get
      {
        return (BaseNotation)GetValue(BaseRepresentationProperty);
      }
      set
      {
        SetValue(BaseRepresentationProperty, value);
      }
    }
    public static readonly DependencyProperty BaseRepresentationProperty =
      DependencyProperty.Register("BaseRepresentation",
      typeof(BaseNotation), typeof(SignalGraph),
      new FrameworkPropertyMetadata(BaseNotation.Hex, new PropertyChangedCallback(ReDraw)));

The Binding is to an object in treeview's itemtemplate.

        >
        <!--Defines panel used by treeview to place items in itemspresenter-->
        <TreeView.ItemsPanel>
          <ItemsPanelTemplate>
            <VirtualizingStackPanel />
          </ItemsPanelTemplate>
        </TreeView.ItemsPanel>


        <!--Template Defining the layout of items in this treeview-->
        <TreeView.ItemTemplate >
          <HierarchicalDataTemplate ItemsSource ="{Binding Path = bits}">
            <Components:SignalGraph 
              x:Name="signal_graph"
              IsSignal="True"
              BaseRepresentation="{Binding Path=BaseRepresentation, Mode=TwoWay}"
              PenWidth="{Binding ElementName=graph_viewer, Path=GraphPenWidth, Mode=OneWay}"
              BusTextColor="{Binding ElementName=graph_viewer, Path=BusTextPenColor, Mode=TwoWay}"
              HighValuePenColor="{Binding ElementName=graph_viewer, Path=HighValuePenColor, Mode=TwoWay}"
              LowValuePenColor="{Binding ElementName=graph_viewer, Path=LowValuePenColor, Mode=TwoWay}"
              UnknownValuePenColor="{Binding ElementName=graph_viewer, Path=UnknownValuePenColor, Mode=TwoWay}"
              Height="{Binding ElementName=graph_viewer, Path=GraphHeight, Mode=OneWay}"
              VerticalAlignment="Stretch"
              Signal="{Binding}" 
              MaxTimeValue="{Binding ElementName=graph_viewer, Path = _SignalDataViewModel.MaxTimeValue}"
              AxisDivisionUnit="{Binding ElementName=graph_viewer, Path = AxisDivisionUnit}"
              MinimumXInDIPs="{Binding ElementName=signal_scrollviewer, Path=HorizontalOffset}"
              ViewportWidth="{Binding ElementName=signal_scrollviewer, Path=ViewportWidth}"
              />
            <HierarchicalDataTemplate.ItemTemplate>
              <DataTemplate>
                <Components:SignalGraph 
                  x:Name="bit_graph"
                  IsSignal="False" 
                  Height="{Binding ElementName=graph_viewer, Path=GraphHeight, Mode=OneWay}"
                  VerticalAlignment="Stretch"
                  BusTextColor="{Binding ElementName=graph_viewer, Path=BusTextPenColor, Mode=TwoWay}"
                  HighValuePenColor="{Binding ElementName=graph_viewer, Path=HighValuePenColor, Mode=TwoWay}"
                  LowValuePenColor="{Binding ElementName=graph_viewer, Path=LowValuePenColor, Mode=TwoWay}"
                  UnknownValuePenColor="{Binding ElementName=graph_viewer, Path=UnknownValuePenColor, Mode=TwoWay}"
                  PenWidth="{Binding ElementName=graph_viewer, Path=GraphPenWidth, Mode=OneWay}"
                  Bit="{Binding}"
                  MaxTimeValue="{Binding RelativeSource = {RelativeSource AncestorType={x:Type DaedalusGraphViewer:GraphViewer}}, Path = _SignalDataViewModel.MaxTimeValue}"
                  AxisDivisionUnit="{Binding ElementName=graph_viewer, Path = AxisDivisionUnit}"
                  MinimumXInDIPs="{Binding ElementName=signal_scrollviewer, Path=HorizontalOffset}"
                  ViewportWidth="{Binding ElementName=signal_scrollviewer, Path=ViewportWidth}"
                  />
              </DataTemplate>
            </HierarchicalDataTemplate.ItemTemplate>
          </HierarchicalDataTemplate>
        </TreeView.ItemTemplate>
      </TreeView>

I have checked the datacontext of signalgraph in the debugger and it is correctly set to signalviewmodel. My output does not have any binding errors. In addition, if I put a break point in the SignalViewModel Class I can see that the OnPropertyChanged Event is being raised.

However, there is no change to the target property when I check it. When I break inside of signalgraph on scrolling, I can check and see that the datacontext's (signalviewmodel's) BaseRepresentation has changed to BaseNotation.UnsignedDecimal. However, the dependency property BaseRepresentation in SignalGraph has not updated to the new value. Why isn't the binding working?

Answer 1

Try

{Binding Path=BaseRepresentation, Mode=TwoWay}

More on data binding modes: http://msdn.microsoft.com/en-us/library/ms752347.aspx (Read "direction of the data flow").

Answer 2

dang it. I can't believe it was such a simple error. i've done this before too without thinking but I had forgotten about it because it had been a while. Never ever ever manually set the property to value in the constructor or elsewhere or you break the binding