是的,您将能够做到这一点。只需从类接口继承您的控件CompositeControl,并将任何扩展程序或控件从 ACT 项目添加到 Controls 集合,就像您应该使用序号 ASP.NET 服务器控件执行此操作一样。您也可以继承现有的控件并实现INamingContainer接口,但在这种情况下,您必须RenderChildren从控件的方法中手动调用Render方法:
[DefaultProperty("Text")]
[ToolboxData("<{0}:WatermarkedTextBox runat=server></{0}:WatermarkedTextBox>")]
public class WatermarkedTextBox : TextBox, INamingContainer
{
    private AjaxControlToolkit.TextBoxWatermarkExtender _watermarkExtender;
    public string WatermarkText
    {
        get
        {
            return ViewState["WatermarkText"] as string;
        }
        set
        {
            ViewState["WatermarkText"] = value;
        }
    }
    protected override void CreateChildControls()
    {
        Controls.Clear();
        this._watermarkExtender = new AjaxControlToolkit.TextBoxWatermarkExtender
        {
            ID = "wte",
            TargetControlID = this.ID,
            WatermarkText = this.WatermarkText
        };
        this.Controls.Add(_watermarkExtender);
    }
    protected override void Render(HtmlTextWriter writer)
    {
        base.Render(writer);
        RenderChildren(writer);
    }
}
}