asp.net怎样绘制柱状趋势图

<%@ Page language="c#" Codebehind="WeekUptrendGif.aspx.cs" AutoEventWireup="false" Inherits="ims_sav.ims_sav_2th.UserInterFace.SafeCheckAndScout.FiveStarCheck.FiveStarEvaluate.WeekUptrendGif"  ContentType="image/gif" %>

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#region 绘制拄状趋势图
/// <summary>
/// 绘制拄状趋势图
/// </summary>
/// <param name="TShowDataTable"></param>
protected void DrawUptrendGif(System.Data .DataTable TShowDataTable)
{
System.Drawing .Bitmap map=new Bitmap (910,470);
System.Drawing .Graphics g=System.Drawing .Graphics .FromImage(map);
System.Drawing .Brush brush=new SolidBrush(Color.White);
g.FillRectangle(brush,0,0,910,470);
            
//绘制总标题
 int titlex0=136+10+130;
 int titley0=9;
System.Drawing.Font f=new Font ("宋体",float.Parse ("12"),System.Drawing .FontStyle .Bold);
brush=new SolidBrush(Color.Black);
            g.DrawString("五星评估得分每周滚动趋势图",f,brush,float.Parse(titlex0.ToString ()),float.Parse(titley0.ToString ()));

//绘制范围框
System.Drawing .Pen p=new Pen (Color.Black);
g.DrawRectangle(p,41,31,790,400);

    //绘制具体显示的标题

if(ViewState["cnp"]!=null)
{

string cnp=(string)ViewState["cnp"];
int titlex=136+10+130;
int titley=31+26;
string title="五星评估每周得分("+cnp+")";
g.DrawString(title,f,brush,float.Parse(titlex.ToString ()),float.Parse(titley.ToString ()));
}

int startx=136+10;
int starty=91+10;
brush=new SolidBrush(Color.Silver);//silver
g.FillRectangle (brush,startx,starty,630,260);

p=new Pen (Color.Black);
brush=new SolidBrush(Color.Black);
f=new Font ("宋体",float.Parse ("12"));
int index=0;
for(index=0;index<11;index++)
{
//注意每行宽为26
int tempy=26*index+starty;
g.DrawLine(p,startx,tempy,startx+630,tempy);
int value1=100-index*10;
 
float tempx=float.Parse (startx.ToString ())-37;
// tempy=tempy-7;
g.DrawString(value1.ToString(),f,brush,tempx,tempy-7);
               

if(value1==100)
{