Asp.net 基础6（自定义控件之ViewState）

构建自定义控件时，需要考虑周全状态管理。

是用ViewState来管理状态

能够保存在ViewState里边的包括一些标准结合类和带有Serializable 标记的类。

下面自定义控件，实现了用viewstate来保存变量。从而显示到客户端

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Collections;

namespace OwnControl
{
    public class BarGrphaControl:Control
    {
        private ArrayList dataDescription;
        private ArrayList dataValues;
        private double max;

        public BarGrphaControl()
        {
            dataDescription = new ArrayList();
            dataValues = new ArrayList();
        }

        public void AddValue(string name, double value)
        {
            dataDescription.Add(name);
            dataValues.Add(value);
            if (value > max)
                max = value;
        }

        protected override void Render(HtmlTextWriter writer)
        {
            writer.AddAttribute(HtmlTextWriterAttribute.Border, "5px");
            writer.RenderBeginTag(HtmlTextWriterTag.Table);
            foreach (object objStr in dataDescription)
            {
                writer.AddAttribute(HtmlTextWriterAttribute.Border, "5px");
                writer.RenderBeginTag(HtmlTextWriterTag.Tr);
                foreach (object objValue in dataValues)
                {
                    writer.AddAttribute(HtmlTextWriterAttribute.Border, "5px");
                    writer.RenderBeginTag(HtmlTextWriterTag.Td);
                    writer.Write(objStr);
                    writer.RenderEndTag();
                    writer.AddAttribute(HtmlTextWriterAttribute.Border, "5px");
                    writer.AddAttribute(HtmlTextWriterAttribute.Style, "background-color:Red");
                    string widthValue=string.Format("{0}px",objValue.ToString());
                    writer.AddAttribute(HtmlTextWriterAttribute.Width, widthValue);
                    writer.RenderBeginTag(HtmlTextWriterTag.Td);
                    writer.RenderEndTag();
                }
                writer.RenderEndTag();
            }
            writer.RenderEndTag();
        }

        protected override void LoadViewState(object savedState)
        {
            if (savedState != null)
            {
                object[] objStae = (object[])savedState;
                if (objStae[0] != null)
                    base.LoadViewState(objStae[0]);
                if (objStae[1] != null)
                    dataDescription = (ArrayList)objStae[1];
                if (objStae[2] != null)
                    dataValues = (ArrayList)objStae[2];
                if (objStae[3] != null)
                    max = (double)objStae[3];
            }
        }

        protected override object SaveViewState()
        {
            object[] objRet = new object[4];
            objRet[0] = base.SaveViewState();
            objRet[1] = dataDescription;
            objRet[2] = dataValues;
            objRet[3] = max;
            return objRet;
        }
    }
}