using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Drawing.Text;

public partial class TemperatureGraph : System.Web.UI.Page
{
    Graphics gfx;
    Bitmap bmp; 
    protected void Page_Load(object sender, EventArgs e)
    {
        bmp = new Bitmap(900, 800);
        gfx = Graphics.FromImage(bmp);
        gfx.Clear(Color.White);
        gfx.SmoothingMode = SmoothingMode.AntiAlias;
        string text = System.IO.File.ReadAllText(@"C:\Documents and Settings\student\Desktop\FYP (Tan Shirlene Chris 071033F)\Project\Website_GreenICT\Temperature.txt");
        string text1 = text.Replace("\r\n", "-");
        string[] str1 = text1.Split('-');
        // Define Points 
        int[] p = new int[str1.Length];
        for (int i = 0; i < p.Length; i++)
        {
            p[i] = (int)Math.Round(double.Parse(str1[i]));
        }

        string text2 = System.IO.File.ReadAllText(@"C:\Documents and Settings\student\Desktop\FYP (Tan Shirlene Chris 071033F)\Project\Website_GreenICT\DateTime.txt");
        string text3 = text.Replace("\r\n", "-");
        string[] str2 = text3.Split('-');
        // Define Points 
        int[] k = new int[str2.Length];
        for (int i = 0; i < k.Length; i++)
        {
            k[i] = (int)Math.Round(double.Parse(str2[i]));
        }
        //int[] k = new int[p.Length];

        Array.Copy(p, k,p.Length);
        Array.Sort(k);

        DrawChart(p, k[k.Length - 1], k[0]);
    }
    private void DrawChart(int[] points, int maxValue, int minValue)
    {
        //Offset (Margin) Values 
        int bottomOffset = 50;
        int topOffset = 30;
        int leftOffset = 60;
        int rightOffset = 10;

        // Taking care of some bookwork (declaring/initializing variables) 
        int maxDataPoints = points.Length;
        int chartHeight = bmp.Height - bottomOffset;
        int chartWidth = bmp.Width - rightOffset;

        // Adjustable Values 
        double adjustedMax = maxValue * .10 + maxValue;
        double adjustedMin = minValue - .50 * minValue;
        double adjustVerticalRatio = (chartHeight - topOffset) / adjustedMax;
        double adjustHorizontalRatio = ((chartWidth - leftOffset) / (maxDataPoints - 1));

        Pen chartPen = new Pen(Color.Orange, 3);
        Pen gridLine = new Pen(Color.LightGray, 1);

        int minYpos = chartHeight - topOffset;
        int maxYpos = 10;

        // Drawing the Lines 
        for (int i = 0; i < maxDataPoints - 1; i++)
        {
            int xPos = Convert.ToInt32(i * adjustHorizontalRatio) + leftOffset;
            int xPos2 = Convert.ToInt32((i + 1) * adjustHorizontalRatio) + leftOffset;

            int yPos = Convert.ToInt32(chartHeight - adjustVerticalRatio * points[i]);
            int yPos2 = Convert.ToInt32(chartHeight - adjustVerticalRatio * points[i + 1]);

            if (points[i] == minValue)
            {
                minYpos = yPos;
            }

            if (points[i] == maxValue)
            {
                maxYpos = yPos;
            }

            gfx.DrawLine(gridLine, new Point(xPos2, topOffset), new Point(xPos2, chartHeight));
            gfx.DrawLine(chartPen, new Point(xPos, yPos), new Point(xPos2, yPos2));

            gfx.DrawString(i.ToString(), new Font("Arial", 8), new SolidBrush(Color.Gray), new Point(xPos - 4, chartHeight + 10));
        }

        //Draw Border Lines 
        Pen borderLine = new Pen(Color.DarkGray, 2);

        //Left Border 
        gfx.DrawLine(borderLine, new Point(leftOffset, chartHeight), new Point(leftOffset, topOffset));

        //Bottom Border 
        gfx.DrawLine(borderLine, new Point(leftOffset, chartHeight), new Point(chartWidth, chartHeight));

        //Right Border 
        gfx.DrawLine(borderLine, new Point(chartWidth, chartHeight), new Point(chartWidth, topOffset));

        //Top Border 
        gfx.DrawLine(borderLine, new Point(leftOffset, topOffset), new Point(chartWidth, topOffset));

        //Drawing Vertical Min/Max Values 
        gfx.DrawString(maxValue.ToString(), new Font("Arial", 8), new SolidBrush(Color.Gray), new Point(leftOffset - 25, maxYpos));
        gfx.DrawString(minValue.ToString(), new Font("Arial", 8), new SolidBrush(Color.Gray), new Point(leftOffset - 25, minYpos));
        gfx.DrawLine(gridLine, new Point(leftOffset - 25, minYpos), new Point(chartWidth, minYpos));
        gfx.DrawLine(gridLine, new Point(leftOffset - 25, maxYpos), new Point(chartWidth, maxYpos));

        // Title 
        gfx.DrawString("[ Temperature Values ]", new Font("Arial", 10, FontStyle.Bold), new SolidBrush(Color.FromArgb(0, 102, 204)), new Point(leftOffset + 60, topOffset - 30));

        //Finalizing and Cleaning Up 
        Response.ContentType = "image/jpeg";
        bmp.Save(Response.OutputStream, ImageFormat.Jpeg);
        bmp.Dispose();
        gfx.Dispose();
        Response.End();
    }
}

Above are my exisiting codes to tabulate Readings.

X-axis showing the Temperature readings itself.(from the textfile also)

Y-axis showing the Number of readings inside the textfile that is adding on every min when the page refresh itself.

This particular textfiles only has the readings.

I have created a new textfiles containing readings together with the date and time.

eg.

22.8 11/11/2009 2:11:34 PM

22.3 11/11/2009 3:34:13 AM

------------------------------------------------

so on so forth in the textfiles.

instead of printing the index of the readings i would like to print the corresponding datetime instead plotted on the graph.

where should i edit the codes on?

I see you have a Linq reference which means you are using .Net 3.5.

There is a free Microsoft Chart component you could use that would make things easier.