C# 指定的元素已经是另一个元素的逻辑子元素。先断开
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Specified element is already the logical child of another element. Disconnect it first
提问by Guillaume Slashy
here is the error I have when I want to attach a FrameworkElement to a new Window to publish it to a PNG file.
这是我想将 FrameworkElement 附加到新窗口以将其发布到 PNG 文件时遇到的错误。
So my idea is to remove the parent-child link, call my method, and add the child again with this code :
所以我的想法是删除父子链接，调用我的方法，并使用以下代码再次添加子项：
this.RemoveLogicalChild(element);
PublishFrameworkElement(element, stream);
this.AddLogicalChild(element);
But I got the exact same error...
但我得到了完全相同的错误...
I looked a lot of questions about this error, here on SO, but none answered to my problem What am I missing ?
我在 SO 上查看了很多有关此错误的问题，但没有人回答我的问题我错过了什么？
EDIT : here is the code that worked for me :
编辑：这是对我有用的代码：
var element = _GeneratedContent as FrameworkElement;
var ParentPanelCollection = (element.Parent as Panel).Children as UIElementCollection;
ParentPanelCollection.Clear();
FileStream stream = [...]
if (element != null)
{
PublishFrameworkElement(element, stream);
ParentPanelCollection.Add(element);
}
stream.Close();
采纳答案by Clemens
If elementis the child of a Panel (e.g. Grid) you have to remove it from the Panel's Childrencollection. If it is set as Contentof a ContentControl, you'd have to set that Content to null (or anything else that is not element).
如果element是面板（例如网格）的子项，则必须将其从面板的子项集合中删除。如果它设置为Contenta ContentControl，则必须将该 Content 设置为 null （或其他任何不是element）。
回答by Piotr Justyna
Guillaume,
纪尧姆，
You can try to additionally use RemoveVisualChildmethod after RemoveLogicalChild:
您可以尝试在RemoveLogicalChild之后额外使用RemoveVisualChild方法：
this.RemoveLogicalChild(element);
this.RemoveVisualChild(element);
PublishFrameworkElement(element, stream);
Hope this helps, Piotr.
希望这会有所帮助，Piotr。
回答by Gerald G.
I had similar but slightly different issue but got the same error message. I made a workaround by making an inherited class and calling RemoveLogicalChild (since this is a protected method).
我有类似但略有不同的问题，但收到相同的错误消息。我通过创建一个继承类并调用 RemoveLogicalChild （因为这是一个受保护的方法）来解决方法。
public partial class PopupWindow : Window
{
public PopupWindow()
{
InitializeComponent();
}
protected override void OnClosed(EventArgs e)
{
base.OnClosed(e);
this.RemoveLogicalChild(this.Content); // since protected method
}
}
It worked for me. I made a simple example you can see here.
它对我有用。我做了一个简单的例子，你可以在这里看到。
http://wpfgrid.blogspot.com/2013/01/wpf-error-specified-element-is-already.html
http://wpfgrid.blogspot.com/2013/01/wpf-error-specified-element-is-already.html
回答by Jamie Mellway
Old question but I didn't have luck with the other answers, so I made a extension method to remove the item from its parent.
老问题，但我对其他答案没有运气，所以我做了一个扩展方法来从它的父项中删除该项目。
public static class FrameworkElementHelper
{
public static void RemoveFromParent(this FrameworkElement item)
{
if (item != null)
{
var parentItemsControl = (ItemsControl)item.Parent;
if (parentItemsControl != null)
{
parentItemsControl.Items.Remove(item as UIElement);
}
}
}
}
