五:理解控件的运行机制(例:基于Control命名空间的简单控件)

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Text;
namespace hellowControl
{
    public class HellowControl:Control
    {
        protected override void Render(HtmlTextWriter writer)
        {
            //要先写div的样式
            writer.AddStyleAttribute(HtmlTextWriterStyle.TextAlign, "center");
            writer.AddStyleAttribute(HtmlTextWriterStyle.Width, "180px");
            writer.AddStyleAttribute(HtmlTextWriterStyle.Height, "180px");
            writer.AddStyleAttribute(HtmlTextWriterStyle.BorderWidth, "1px");
            writer.AddStyleAttribute(HtmlTextWriterStyle.BorderStyle, "solid");
            writer.AddStyleAttribute(HtmlTextWriterStyle.BorderColor, "grey");
            //再写div开始标签
            writer.RenderBeginTag(HtmlTextWriterTag.Div);
            //开始写div里的内容,是一个图片
            //先写图片的样式和属性
            writer.AddAttribute(HtmlTextWriterAttribute.Src, "noimage_s.jpg");
            writer.AddStyleAttribute(HtmlTextWriterStyle.Margin, "8px");
            //写image标签开始
            writer.RenderBeginTag(HtmlTextWriterTag.Img);
            //闭合image标签
            writer.RenderEndTag();
            //闭合div标签
            writer.RenderEndTag();
        }
    }
}