3. 如何实现自定义用户控件(复合控件),自定义事件如何实现?简述委托原理

class Longn : WebControl, IPostBackEventHandler, INamingContainer
{
public Longn()
: base(HtmlTextWriterTag.Div)
{ }

private string Text
{
get;
set;
}
protected override void RenderContents(HtmlTextWriter writer)
{
writer.AddAttribute(HtmlTextWriterAttribute.Value, Text);
writer.AddAttribute(HtmlTextWriterAttribute.Name, this.ClientID);
writer.AddAttribute(HtmlTextWriterAttribute.Type, "text");
writer.RenderBeginTag(HtmlTextWriterTag.Input);
writer.AddAttribute(HtmlTextWriterAttribute.Onclick,Page.ClientScript.GetPostBackEventReference(this,"onclick"));
writer.AddAttribute(HtmlTextWriterAttribute.Value, "确定");
writer.AddAttribute(HtmlTextWriterAttribute.Type, "button"