自定义复合控件[5]获取包含的文本

using System;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;

namespace csMathControl
{
    /// <summary>
    /// Center 的摘要说明。
    /// </summary>
    [DefaultProperty("Text"), 
        ToolboxData("<{0}:Center runat=server></{0}:Center>")]
    [ParseChildren(false)]
    public class Center : System.Web.UI.WebControls.WebControl,INamingContainer
    {
        private string text;
    
        [Bindable(true), 
            Category("Appearance"), 
            DefaultValue("")] 
        public string Text 
        {
            get
            {
                return text;
            }

            set
            {
                text = value;
            }
        }

        /// <summary> 
        /// 将此控件呈现给指定的输出参数。
        /// </summary>
        /// <param name="output"> 要写出到的 HTML 编写器 </param>
        protected override void Render(HtmlTextWriter output)
        {
            //output.Write(Text);
            output.AddAttribute("align","center");
            output.AddStyleAttribute("BackGround-color","red");
            //pannel开始
            output.RenderBeginTag("div");
            foreach(Control ctrItem in Controls)
            {
                ctrItem.RenderControl(output);
            }
            output.RenderEndTag();
        }
        }
}