FrameworkElement.RemoveLogicalChild(Object) 方法

定義

從這個項目的邏輯樹狀結構中移除提供的物件。Removes the provided object from this element's logical tree. FrameworkElement 更新受影響的邏輯樹狀結構父指標,以便與刪除保持同步。FrameworkElement updates the affected logical tree parent pointers to keep in sync with this deletion.

protected public:
 void RemoveLogicalChild(System::Object ^ child);
protected internal void RemoveLogicalChild (object child);
member this.RemoveLogicalChild : obj -> unit
Protected Friend Sub RemoveLogicalChild (child As Object)

參數

child
Object

要移除的項目。The element to remove.

範例

下列範例 Child 會在自訂上 FrameworkElement 執行本身的視覺分層執行的屬性。The following example implements a Child property on a custom FrameworkElement that does its own visual layer implementation. 屬性的 setter 經過設計,因此,如果值變更,舊值會從邏輯樹狀結構中移除,也會從特定類別的視覺集合中移除。The property's setter is designed so that if the value changes, the old value is removed from the logical tree, as well as a class-specific visual collection. 系統會快取這些值,然後將新的值加入標準 WPF 架構層級的邏輯樹狀結構和自訂視覺效果集合中。The values are cached, and then the new value is added to both the standard WPF framework level logical tree and the custom visual collection.

public virtual UIElement Child
{
    get
    {
        return _child;
    }
    set
    {
        if (_child != value)
        {
            //need to remove old element from logical tree
            if (_child != null)
            {
                OnDetachChild(_child);
                RemoveLogicalChild(_child);
            }

            _vc.Clear();

            if (value != null)
            {
                //add to visual
                _vc.Add(value);
                //add to logical
                AddLogicalChild(value);
            }

            //always add the overlay child back into the visual tree if its set
            if (_overlayVisual != null)
                _vc.Add(_overlayVisual);

            //cache the new child
            _child = value;

            //notify derived types of the new child
            if (value != null)
                OnAttachChild(_child);

            InvalidateMeasure();
        }
    }
}
<System.ComponentModel.DefaultValue(GetType(Object), Nothing)>
Public Overridable Property Child() As UIElement
    Get
        Return _child
    End Get
    Set(ByVal value As UIElement)
        If _child IsNot value Then
            'need to remove old element from logical tree
            If _child IsNot Nothing Then
                OnDetachChild(_child)
                RemoveLogicalChild(_child)
            End If

            _vc.Clear()

            If value IsNot Nothing Then
                'add to visual
                _vc.Add(value)
                'add to logical
                AddLogicalChild(value)
            End If

            'always add the overlay child back into the visual tree if its set
            If _overlayVisual IsNot Nothing Then
                _vc.Add(_overlayVisual)
            End If

            'cache the new child
            _child = value

            'notify derived types of the new child
            If value IsNot Nothing Then
                OnAttachChild(_child)
            End If

            InvalidateMeasure()
        End If
    End Set
End Property

備註

使用這個方法,在代表專案邏輯子系的物件上執行集合。Use this method for the implementation of collections on objects that represent logical children of an element. 這可能會在屬性 getter 或 setter、事件、函式的類別處理常式, Changed 或在集合類型本身內完成。This might be done in property getters or setters, class handlers of Changed events, constructors, or within the collection types themselves.

對於控制項作者,除非提供的基底控制項類別的內容模型不適用,否則不建議在此層級操作邏輯樹狀結構。For control authors, manipulating the logical tree at this level is not the recommended practice, unless none of the provided base control class' content models are appropriate. 請考慮在、和層級進行子類別化 ContentControl ItemsControl HeaderedItemsControlConsider subclassing at the level of ContentControl, ItemsControl, and HeaderedItemsControl. 這些類別會透過專用的 Api,提供特殊強制執行邏輯子系的內容模型,以及在 WPFWPF 控制項(例如透過範本設定樣式)中所需的其他功能的支援。These classes provide a content model with particular enforcement of logical children through dedicated APIs, as well as support for other features typically desirable in a WPFWPF control such as styling through templates.

適用於

另請參閱