数据绑定到属性有效，但无法更新

Question

I have property in model:

private EditorSelectionTool SelectionTool { get; set; }

Binding:

 <DataTemplate DataType="{x:Type viewModels:EditorSelectionTool}">
                    <Rectangle Stroke="White" StrokeThickness="1" StrokeDashArray="4 4" Width="{Binding Width}" Height="{Binding Height}" Visibility="{Binding Visibility}"/>
                </DataTemplate>

Model is derivated from PropertyChangedBase class (Caliburn.Micro)

And method which change the property fields:

 public void StartSelecting(Point point)
    {
        SelectionTool.X = point.X;
        SelectionTool.Y = point.Y;
        NotifyOfPropertyChange(() => SelectionTool);
    }

Debug shows that method was called. But change in UI is not happening.

SelectionTool class:

   public class EditorSelectionTool
{
    public double X { get; set; }
    public double Y { get; set; }
    public double Width { get; set; }
    public double Height { get; set; }
    public Visibility Visibility { get; set; }
}

Answer 1

You're firing the property changed event on a property called SelectionTool. However you've never fired the property changed event on Height and Visibility.

In some cases this would work--it depends on if something is actually bound to SelectionTool. In such a case it would force the bindings further "down the chain" to also reload. But since you're having problems, I assume that doesn't apply to your specific binding scenario.

In Visual Studio, the output window often has information about binding failures.

Answer 2

Seeing you are using Caliburn.Micro, you will need to update your EditorSelectionTool to implement PropertyChangedBase and as Paul K mentioned, add property change notifications to each property.

public class EditorSelectionTool : PropertyChangedBase 
{
    private double _x;
    private double _y;
    private double _width;
    private double _height;
    private Visibility _visibility;

    public double X
    {
        get { return _x; }
        set
        {
            _x = value;
            NotifyOfPropertyChange(()=> X);
        }
    }

    public double Y
    {
        get { return _y; }
        set
        {
            _y = value;
            NotifyOfPropertyChange(() => Y);
        }
    }

    public double Width
    {
        get { return _width; }
        set
        {
            _width = value;
            NotifyOfPropertyChange(() => Width);
        }
    }

    public double Height
    {
        get { return _height; }
        set
        {
            _height = value;
            NotifyOfPropertyChange(() => Height);
        }
    }

    public Visibility Visibility
    {
        get { return _visibility; }
        set
        {
            _visibility = value;
            NotifyOfPropertyChange(() => Visibility);
        }
    }
}

Answer 3

You notify a change on SettingTool , but that property has not changed at all. It is the same instance and therefore there is no change.

And even if you notify a change, WPF will check, if there is really a change by comparing the old with the current value (here the instance of SettingTool ).

1. Create a new instance of EditorSelectionTool , assign this to the property and notify the change

or

2. Implement a change notification on each property in EditorSelectionTool