自定义复合控件[3]获取客户信息

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

namespace csMathControl
{
    /// <summary>
    /// 从客户端获取数据
    /// </summary>
    [DefaultProperty("Text"), 
        ToolboxData("<{0}:RenderPostBackText runat=server></{0}:RenderPostBackText>")]
    [DefaultEvent("Change")]
    public class RenderPostBackText : System.Web.UI.WebControls.WebControl,IPostBackDataHandler
    {    
        [Bindable(true), 
            Category("Appearance"), 
            DefaultValue("")] 
        public string Text 
        {
            get
            {
                if(ViewState["text"]!=null)
                return ViewState["text"].ToString();
                else
                    return null;
            }

            set
            {
                ViewState["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("value",this.Text );
            output.AddAttribute("name",this.UniqueID);//[2]必须将这个属性定义成允许使用回递数据
            output.RenderBeginTag("INPUT");
            output.RenderEndTag();
        }
        public event EventHandler Change;
        protected virtual void OnChange(EventArgs e)
        {
            if(Change!=null)
                Change(this,e);
        }
        #region IPostBackDataHandler 成员

        public void RaisePostDataChangedEvent()
        {
            // TODO:  添加 RenderPostBackText.RaisePostDataChangedEvent 实现
            OnChange(EventArgs.Empty);
        }

        public bool LoadPostData(string postDataKey, System.Collections.Specialized.NameValueCollection postCollection)
        {
            // TODO:  添加 RenderPostBackText.LoadPostData 实现
            //return false;
            //如果用户该便了文本就更新文本属性
            if(this.Text!=postCollection[postDataKey])
            {
                this.Text=postCollection[postDataKey];
                //返回true就会调用上面的RaisePostDataChangeEvent
                return true;

            }
            else
                return false;
        }

        #endregion
    }
}