我正在尝试在 WPF 中创建一个只读附加属性,该属性将计算控件的总可视子项数。这样做的好处对我来说并不重要,它能够正确使用附加属性!
首先我已经这样声明了我的属性(property):
internal static readonly DependencyPropertyKey TotalChildCountPropertyKey =
DependencyProperty.RegisterAttachedReadOnly("TotalChildCount", typeof(int), typeof(MyAttachClass), new FrameworkPropertyMetadata(0));
public static readonly DependencyProperty TotalChildCountProperty = TotalChildCountPropertyKey.DependencyProperty;
public static int GetTotalChildCount(DependencyObject obj)
{
return (int)obj.GetValue(TotalChildCountProperty);
}
public static void SetTotalChildCount(DependencyObject obj, int value)
{
obj.SetValue(TotalChildCountPropertyKey, value);
}
我还有一个递归方法声明在其他地方,像这样:
public static class Recursive
{
public static IEnumerable<DependencyObject> GetAllChildren(DependencyObject obj)
{
List<DependencyObject> col = new List<DependencyObject>();
GetAllChildrenImp(obj, col);
return col;
}
private static void GetAllChildrenImp(DependencyObject current, List<DependencyObject> col)
{
if (current != null)
{
col.Add(current);
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(current); i++ )
{
GetAllChildrenImp(VisualTreeHelper.GetChild(current, i), col);
}
}
}
}
现在我想使用此方法为 GetTotalChildCount 属性赋值,但我想不出最好的方法。我可以向依赖项属性更改添加一个事件处理程序,但这永远不会触发,因为我只会读取 xaml 中的值。
这是我在 xaml 中使用它的方式:
<TextBox DataContext="{RelativeSource Self}" Text="{Binding local:MyAttachClass.TotalChildCount}"></TextBox>
总结一下。我希望设置一个 DependencyObjects TotalChildCount 附加属性,然后能够在 xaml 中绑定(bind)到它。就目前而言,这是行不通的,GetTotalChildCount 甚至都没有受到影响。
哦,这是我的第一个问题,希望我足够清楚
最佳答案
你可以这样试试
附加属性
public class MyAttachClass
{
public static readonly DependencyProperty TotalChildCountProperty = DependencyProperty.RegisterAttached("TotalChildCount", typeof(int), typeof(MyAttachClass),
new PropertyMetadata(-1, OnTotalChildCountChanged));
public static int GetTotalChildCount(DependencyObject obj)
{
return (int)obj.GetValue(TotalChildCountProperty);
}
public static void SetTotalChildCount(DependencyObject obj, int value)
{
obj.SetValue(TotalChildCountProperty, value);
}
public static void OnTotalChildCountChanged(object sender, DependencyPropertyChangedEventArgs e)
{
TextBox txt = sender as TextBox;
if (txt != null)
{
var children = Recursive.GetAllChildren(txt);
txt.Text = children.Count().ToString();
}
}
}
而 xaml 为
<TextBox local:MyAttachClass.TotalChildCount="0" ></TextBox>
希望对您有所帮助!
关于c# - 在 WPF 中使用附加属性,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/33963378/