将控件添加到设计器中用户控件上的面板

除了我关于使用具有Panel覆盖SelectionRules属性的自己的设计器的派生的评论之外，另一种方法是利用设计器的ISelectionService来检测所选组件中的更改，如果它被选中，则删除面板。

这是通过覆盖控件的Site属性来设置挂钩来实现的。另请注意，我将InternalPanel属性更改为只读，因为您确实不希望该属性可写。

[DesignerAttribute(typeof(MyControlDesigner))]
[Designer("System.Windows.Forms.Design.ParentControlDesigner, System.Design", typeof(IDesigner))]
public partial class ucInput : UserControl
{

    [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
    public Panel InternalPanel
    {
        get { return pnlContent; }
    }

    public ucInput()
    {
        InitializeComponent();
    }

    private ISelectionService selectionService;
    private IDesignerHost host;
    public override ISite Site
    {
        get
        {
            return base.Site;
        }
        set
        {
            host = null;
            UnSubscribeFromSelectionService();
            base.Site = value;
            if (value != null)
            {
                host = (IDesignerHost)this.Site.GetService(typeof(IDesignerHost));
                if (host != null)
                {
                    if (host.Loading)
                    {
                        // defer subscription to selection service until fully loaded
                        host.Activated += Host_Activated;
                    }
                    else
                    {
                        SubscribeToSelectionService();
                    }
                }
            }
        }
    }

    private void Host_Activated(object sender, EventArgs e)
    {
        host.Activated -= Host_Activated;
        SubscribeToSelectionService();
    }

    private void SubscribeToSelectionService()
    {
        selectionService = (ISelectionService)this.Site.GetService(typeof(ISelectionService));
        if (selectionService != null)
        {
            selectionService.SelectionChanging += OnSelectionChanging;
        }
    }

    private void UnSubscribeFromSelectionService()
    {
        if (selectionService != null)
        {
            selectionService.SelectionChanging -= OnSelectionChanging;
        }
    }

    private void OnSelectionChanging(object sender, EventArgs e)
    {
        if (selectionService.GetComponentSelected(pnlContent))
        {
            selectionService.SelectionChanging -= OnSelectionChanging;
            selectionService.SetSelectedComponents(new[] { pnlContent }, SelectionTypes.Remove);
            selectionService.SelectionChanging += OnSelectionChanging;
        }
    }
}

编辑：原始代码忽略SelectionService了IDesignerHost在加载时不可用的原因。添加了将订阅推迟到IDesignerHost激活的代码。