LL Mathematical Parser

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using MathParserDataStructures;
using System.Diagnostics;
namespace MathParser.v._3
{
    public partial class Parser : Form
    {
        Bitmap bitmap = null;
        public Parser()
        {
            InitializeComponent();
        }

        private void Parser_Load(object sender, EventArgs e)
        {
            _imagePanel.Location = new Point(this.ClientRectangle.Width / 2, 5);
            btnDraw.Location = new Point(_imagePanel.Width - (btnDraw.Width + 18), btnDraw.Location.Y);
            _btnClear.Location = new Point(_imagePanel.Width - (btnDraw.Width + 18), btnDraw.Location.Y + btnDraw.Size.Height + 5);
            _btnSave.Location = new Point(_imagePanel.Width - (btnDraw.Width + 18), btnDraw.Location.Y + btnDraw.Size.Height + _btnClear.Height + 10); 
            _imagePanel.Width = this.ClientRectangle.Width / 2 - 5;
            _imagePanel.Height = this.ClientRectangle.Height - 10;
            _tbFunction.Width = _imagePanel.Width - 8;
        }

        private void Parser_Paint(object sender, PaintEventArgs e)
        {
            this.DrawCoordinates();
        }

        private void DrawCoordinates()
        {
            int width = this._imagePanel.Width;
            int height = this._imagePanel.Height;
            int tenthHeigth = height / 10;
            int tenthWidth = width / 10;
            int penWidth = 3;
            Color penColor = Color.Red;
            if (height == 0 || width == 0)
                return;
            bitmap = new Bitmap(width, height);
            Graphics g = Graphics.FromImage(bitmap); 
            
            g.Clear(this.BackColor);
            Pen pen = new Pen(penColor, penWidth);

            pen.EndCap = System.Drawing.Drawing2D.LineCap.ArrowAnchor;

            Point startPointVertical = new Point(tenthWidth, height - tenthHeigth);
            Point endPointVertical = new Point(tenthWidth, tenthHeigth);

            Point startPointHorizontal = startPointVertical;
            Point endPointHorizontal = new Point(width - tenthWidth, height - tenthHeigth);

            g.DrawLine(pen, startPointVertical, endPointVertical);
            g.DrawLine(pen, startPointHorizontal, endPointHorizontal);

            Font f = new Font(this._tbFunction.Font, FontStyle.Italic);
            Brush b = Brushes.Red;
            float offsetX = ((float)(endPointHorizontal.X - startPointHorizontal.X)) / 8;
            float offsetY = ((float)(startPointVertical.Y - endPointVertical.Y)) / 8;
            for (int i = 0; i <= 8; i++)
            {
                PointF p1 = new PointF((i * offsetX)+tenthWidth-5, startPointHorizontal.Y + 10);
                PointF p2 = new PointF(startPointVertical.X-20, i*offsetY+tenthHeigth-5);
                g.DrawString(i.ToString(), f, b, p1);
                g.DrawString((8-i).ToString(), f, b, p2);
            }

            this.CreateGraphics().DrawImage(bitmap, 0, 0);
            if (!String.IsNullOrEmpty(this._tbFunction.Text))
                btnDraw_Click(null, null);

        }

        private void Parser_Resize(object sender, EventArgs e)
        {
            _imagePanel.Location = new Point(this.ClientRectangle.Width/2, 5);
           _imagePanel.Width = this.ClientRectangle.Width / 2 - 5;
            _imagePanel.Height = this.ClientRectangle.Height - 10;
            btnDraw.Location = new Point(_imagePanel.Width - (btnDraw.Width + 5), btnDraw.Location.Y);
            _btnClear.Location = new Point(_imagePanel.Width - (btnDraw.Width + 5), btnDraw.Location.Y + btnDraw.Size.Height+5);
            _btnSave.Location = new Point(_imagePanel.Width - (btnDraw.Width + 5), btnDraw.Location.Y + btnDraw.Size.Height + _btnClear.Height + 10); 
            _tbFunction.Width = _imagePanel.Width - 8;
        }

        private void btnDraw_Click(object sender, EventArgs e)
        {
            int numberOfPoints = 500;
            string mathFunction = this._tbFunction.Text;
            if (String.IsNullOrEmpty(mathFunction))
                return;
            MathObj mathObj = new MathObj();
            PointF[] lineFunc = new PointF[numberOfPoints];
            int width = this._imagePanel.Width;
            int height = this._imagePanel.Height;
            int tenthHeigth = height / 10;
            int tenthWidth = width / 10;
            float offset = ((float)width * 10 / 10) / numberOfPoints;
            int startX= 0, endX = 10;
            double offsetX  = (double)(endX-startX)/numberOfPoints;
            double xVal = 0;

            char [] variablesArray = new char[1] { 'x' };
            double [] valuesArray = new double[1];

            for (int i = 0; i < numberOfPoints; i++)
            {
                lineFunc[i].X = tenthWidth + (float)(offset * (i + 1));
                
                try
                {/*
                  * ----------------------------------------
                  * Actual Mathematical calculation is here
                  * ----------------------------------------
                  */
                    valuesArray[0] = xVal;
                    lineFunc[i].Y = (height - tenthHeigth) - tenthHeigth * (float)mathObj.Evaluate(mathFunction, variablesArray, valuesArray);
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                    return;
                }
                if (lineFunc[i].X > width || lineFunc[i].Y > height)
                {
                    lineFunc[i].X = lineFunc[i - 1].X;
                    lineFunc[i].Y = lineFunc[i - 1].Y;
                }

           // Debug.WriteLine("X: " + lineFunc[i].X.ToString() + " Y:" + lineFunc[i].Y.ToString());
                xVal += offsetX;
            }
           // Debug.WriteLine("tenthHeigth=" + tenthHeigth.ToString());
           // Debug.WriteLine("height=" + height.ToString());
            try
            {
                Graphics g = Graphics.FromImage(bitmap);
                g.DrawLines(new Pen(Color.Blue), lineFunc);
                this.CreateGraphics().DrawImage(bitmap, 0, 0);
            }
            catch (System.OverflowException ex)
            {
                MessageBox.Show("Could not draw the graph: " + ex.Message,"Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
           
        }

        private void _btnClear_Click(object sender, EventArgs e)
        {
            this._tbFunction.Text = "";
            this.DrawCoordinates();
        }

        private void _btnSave_Click(object sender, EventArgs e)
        {
            SaveFileDialog s = new SaveFileDialog();
            s.FileName = "sample.jpg";
            s.Filter = "*.jpg|*.jpg";
            if (s.ShowDialog() == DialogResult.OK)
            {
                string path = s.FileName;
                bitmap.Save(path);
            }
        }

   
    }
}