嗯,重申我上面的评论,想必你有这样的事情
public class PathViewModel
{
public ObservableCollection<Point> Points { get; private set; }
PathViewModel ()
{
Points = new ObservableCollection<Point> ();
}
}
只需通过实现来扩展此模型INotifyPropertyChanged
,并为路径中的最后一个点创建一个显式属性,
public class PathViewModel : INotifyPropertyChanged
{
private static readonly PropertyChangedEventArgs OmegaPropertyChanged =
new PropertyChangedEventArgs ("Omega");
// returns true if there is at least one point in list, false
// otherwise. useful for disambiguating against an empty list
// (for which Omega returns 0,0) and real path coordinate
public bool IsOmegaDefined { get { return Points.Count > 0; } }
// gets last point in path, or 0,0 if no points defined
public Point Omega
{
get
{
Point omega;
if (IsOmegaDefined)
{
omega = Points[Points.Count - 1];
}
return omega;
}
}
// gets points in path
public ObservableCollection<Point> Points { get; private set; }
PathViewModel ()
{
Points = new ObservableCollection<Point> ();
}
// interfaces
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
#endregion
// private methods
private void Points_CollectionChanged (
object sender,
NotifyCollectionChangedEventArgs e)
{
// if collection changed, chances are so did Omega!
if (PropertyChanged != null)
{
PropertyChanged (this, OmegaPropertyChanged);
}
}
}
唯一值得注意的是在集合更改时触发属性更改事件。这会通知 WPF 模型已更改。
现在,在 Xaml 土地上,
<!-- assumes control's DataContext is set to instance of PathViewModel -->
<Path
Stroke="Black"
x:Name="path1"
Data="{Binding Path=Points}"
Margin="0"
StrokeThickness="4"/>
<!-- or whatever control you like, button to demonstrate binding -->
<Button
Content="{Binding Path=Omega}"
IsEnabled="{Binding Path=IsOmegaDefined}"/>
好的,所以IsEnabled
上面不会隐藏图像\按钮,但绑定到Visibility
是一个简单的问题:a)更改我们的视图模型以公开可见性属性,或 b)绑定到将我们的布尔值转换为可见性枚举的值转换器.
希望这可以帮助!:)