Currency Calculator

Question

Hiya all, This Currency Calculator i spend few weeks on it, its complete code to run in Microsoft Visual Studio 2008. but its not working fully. i remove so many errors now i dont get any Error in Debug but few strange thing when i run the program..for example i cant input . decimal anyhow some one help me please i just give up on it.....but i will keep trying and i will try to ask some friends.. Kindly help me if you can
Many Thank. there is no error in code thats why i cant point out where is the problem in code.
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Form1.cs
-----------------------------------------------------------
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.IO;
using System.Windows.Forms;
namespace testbaby
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void btnBack_Click(object sender, EventArgs e)
        {
            this.txtDisplay.Text = (decimal.Parse(this.txtDisplay.Text) / decimal.Parse(this.txtRate.Text)).ToString("N");
            this.just_cleared = true;
        }
        private void btnBackspace_click(object sender, EventArgs e)
        {
            if (this.txtDisplay.Text.Length > 1)
            {
                this.txtDisplay.Text = this.txtDisplay.Text.Substring(0, this.txtDisplay.Text.Length - 1);
            }
            else
            {
                this.txtDisplay.Text = "0";
                this.just_cleared = true;
               
            }
        }
        private void btnForward_Click(object sender, EventArgs e)
        {
            this.txtDisplay.Text = (decimal.Parse(this.txtDisplay.Text) * decimal.Parse(this.txtRate.Text)).ToString("N");
            this.just_cleared = true;
        }
        private void btnPoint_Click(object sender, EventArgs e)
        {
            this.txtDisplay.AppendText(".");
            this.just_cleared = false;
        }
        private void Button0_Click(object sender, EventArgs e)
        {
            if (this.just_cleared)
            {
                this.txtDisplay.Text = "0";
            }
            else if (this.txtDisplay.Text.Length < 9)
            {
                this.txtDisplay.AppendText("0");
            }
        }
        private void Button1_Click(object sender, EventArgs e)
        {
            if (this.just_cleared)
            {
                this.txtDisplay.Text = "1";
                this.just_cleared = false;
            }
            else if ((this.txtDisplay.Text != "0") && (this.txtDisplay.Text.Length < 9))
            {
                this.txtDisplay.AppendText("1");
            }
        }
        private void Button2_Click(object sender, EventArgs e)
        {
            if (this.just_cleared)
            {
                this.txtDisplay.Text = "2";
                this.just_cleared = false;
            }
            else if (this.txtDisplay.Text.Length < 9)
            {
                this.txtDisplay.AppendText("2");
            }
        }
        private void Button3_Click(object sender, EventArgs e)
        {
            if (this.just_cleared)
            {
                this.txtDisplay.Text = "3";
                this.just_cleared = false;
            }
            else if (this.txtDisplay.Text.Length < 9)
            {
                this.txtDisplay.AppendText("3");
            }
        }
        private void Button4_Click(object sender, EventArgs e)
        {
            if (this.just_cleared)
            {
                this.txtDisplay.Text = "4";
                this.just_cleared = false;
            }
            else if (this.txtDisplay.Text.Length < 9)
            {
                this.txtDisplay.AppendText("4");
            }
        }
        private void Button5_Click(object sender, EventArgs e)
        {
            if (this.just_cleared)
            {
                this.txtDisplay.Text = "5";
                this.just_cleared = false;
            }
            else if (this.txtDisplay.Text.Length < 9)
            {
                this.txtDisplay.AppendText("5");
            }
        }
        private void Button6_Click(object sender, EventArgs e)
        {
            if (this.just_cleared)
            {
                this.txtDisplay.Text = "6";
                this.just_cleared = false;
            }
            else if (this.txtDisplay.Text.Length < 9)
            {
                this.txtDisplay.AppendText("6");
            }
        }
        private void Button7_Click(object sender, EventArgs e)
        {
            if (this.just_cleared)
            {
                this.txtDisplay.Text = "7";
                this.just_cleared = false;
            }
            else if (this.txtDisplay.Text.Length < 9)
            {
                this.txtDisplay.AppendText("7");
            }
        }
        private void Button8_Click(object sender, EventArgs e)
        {
            if (this.just_cleared)
            {
                this.txtDisplay.Text = "8";
                this.just_cleared = false;
            }
            else if (this.txtDisplay.Text.Length < 9)
            {
                this.txtDisplay.AppendText("8");
            }
        }
        private void Button9_Click(object sender, EventArgs e)
        {
            if (this.just_cleared)
            {
                this.txtDisplay.Text = "9";
                this.just_cleared = false;
            }
            else if (this.txtDisplay.Text.Length < 9)
            {
                this.txtDisplay.AppendText("9");
            }
        }
        private void chkLock_CheckedChanged(object sender, EventArgs e)
        {
            if (this.chkLock.Checked)
            {
                this.txtRate.BackColor = Color.Silver;
                this.txtRate.ReadOnly = true;
               
            }
            else
            {
                this.txtRate.BackColor = Color.White;
                this.txtRate.ReadOnly = false;
               
            }
        }
        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            string startupPath = Application.StartupPath;
            try
            {
                StreamWriter writer = new StreamWriter(startupPath + @"\ccrate.dat");
                writer.WriteLine(this.txtRate.Text);
                writer.Close();
            }
            catch
            {
            }
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            string startupPath = Application.StartupPath;
            if (File.Exists(startupPath + @"\ccrate.dat"))
            {
                StreamReader reader = new StreamReader(startupPath + @"\ccrate.dat");
                this.txtRate.Text = reader.ReadLine();
                reader.Close();
            }
            else
            {
                this.txtRate.Text = "1.0";
            }
        }
        private void button2_Click(object sender, EventArgs e)
        {
        }
        private void txtDisplay_TextChanged(object sender, EventArgs e)
        {
            this.btnPoint.Enabled = !this.txtDisplay.Text.Contains(".");
        }
        private void txtRate_Leave(object sender, EventArgs e)
        {
           
            try
            {
                double num = double.Parse(this.txtRate.Text);
                if (num > 0.0001)
                {
                    this.txtRate.Text = num.ToString();
                    this.old_rate = num;
                    this.txtDisplay.Text = "0";
                    this.just_cleared = true;
                }
                else
                {
                    this.txtRate.Text = this.old_rate.ToString();
                }
            }
            catch
            {
                this.txtRate.Text = this.old_rate.ToString();
            }
        }
    }
}
-----------------------------------------------------------------------
form1.Designer.cs
-----------------------------------------------------------------------
namespace testbaby
{
    partial class Form1
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }
        #region Windows Form Designer generated code
        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(Form1));
            this.txtDisplay = new System.Windows.Forms.TextBox();
            this.btnBackspace = new System.Windows.Forms.Button();
            this.Button0 = new System.Windows.Forms.Button();
            this.Button1 = new System.Windows.Forms.Button();
            this.button2 = new System.Windows.Forms.Button();
            this.button3 = new System.Windows.Forms.Button();
            this.button4 = new System.Windows.Forms.Button();
            this.button5 = new System.Windows.Forms.Button();
            this.button6 = new System.Windows.Forms.Button();
            this.button7 = new System.Windows.Forms.Button();
            this.button8 = new System.Windows.Forms.Button();
            this.button9 = new System.Windows.Forms.Button();
            this.chkLock = new System.Windows.Forms.CheckBox();
            this.txtRate = new System.Windows.Forms.TextBox();
            this.label1 = new System.Windows.Forms.Label();
            this.btnBack = new System.Windows.Forms.Button();
            this.btnForward = new System.Windows.Forms.Button();
            this.btnClear = new System.Windows.Forms.Button();
            this.btnPoint = new System.Windows.Forms.Button();
            this.SuspendLayout();
            //
            // txtDisplay
            //
            this.txtDisplay.BackColor = System.Drawing.Color.Black;
            this.txtDisplay.Font = new System.Drawing.Font("Microsoft Sans Serif", 12F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.txtDisplay.ForeColor = System.Drawing.Color.Lime;
            this.txtDisplay.Location = new System.Drawing.Point(26, 16);
            this.txtDisplay.Name = "txtDisplay";
            this.txtDisplay.Size = new System.Drawing.Size(155, 26);
            this.txtDisplay.TabIndex = 0;
            this.txtDisplay.TextChanged += new System.EventHandler(this.txtDisplay_TextChanged);
            //
            // btnBackspace
            //
            this.btnBackspace.Font = new System.Drawing.Font("Microsoft Sans Serif", 10.25F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.btnBackspace.Image = ((System.Drawing.Image)(resources.GetObject("btnBackspace.Image")));
            this.btnBackspace.Location = new System.Drawing.Point(143, 87);
            this.btnBackspace.Name = "btnBackspace";
            this.btnBackspace.Size = new System.Drawing.Size(38, 64);
            this.btnBackspace.TabIndex = 62;
            this.btnBackspace.Text = "z";
            this.btnBackspace.UseVisualStyleBackColor = true;
            this.btnBackspace.Click += new System.EventHandler(this.btnBackspace_click);
            //
            // Button0
            //
            this.Button0.BackColor = System.Drawing.SystemColors.ActiveBorder;
            this.Button0.Location = new System.Drawing.Point(29, 180);
            this.Button0.Name = "Button0";
            this.Button0.Size = new System.Drawing.Size(70, 24);
            this.Button0.TabIndex = 2;
            this.Button0.Text = "0";
            this.Button0.UseVisualStyleBackColor = false;
            this.Button0.Click += new System.EventHandler(this.Button0_Click);
            //
            // Button1
            //
            this.Button1.Location = new System.Drawing.Point(29, 147);
            this.Button1.Name = "Button1";
            this.Button1.Size = new System.Drawing.Size(32, 24);
            this.Button1.TabIndex = 63;
            this.Button1.Text = "1";
            this.Button1.UseVisualStyleBackColor = true;
            this.Button1.Click += new System.EventHandler(this.Button1_Click);
            //
            // button2
            //
            this.button2.Location = new System.Drawing.Point(67, 147);
            this.button2.Name = "button2";
            this.button2.Size = new System.Drawing.Size(32, 24);
            this.button2.TabIndex = 64;
            this.button2.Text = "2";
            this.button2.UseVisualStyleBackColor = true;
            this.button2.Click += new System.EventHandler(this.button2_Click);
            //
            // button3
            //
            this.button3.Location = new System.Drawing.Point(105, 147);
            this.button3.Name = "button3";
            this.button3.Size = new System.Drawing.Size(32, 24);
            this.button3.TabIndex = 65;
            this.button3.Text = "3";
            this.button3.UseVisualStyleBackColor = true;
            this.button3.Click += new System.EventHandler(this.Button3_Click);
            //
            // button4
            //
            this.button4.Location = new System.Drawing.Point(29, 117);
            this.button4.Name = "button4";
            this.button4.Size = new System.Drawing.Size(32, 24);
            this.button4.TabIndex = 66;
            this.button4.Text = "4";
            this.button4.UseVisualStyleBackColor = true;
            this.button4.Click += new System.EventHandler(this.Button4_Click);
            //
            // button5
            //
            this.button5.Location = new System.Drawing.Point(67, 117);
            this.button5.Name = "button5";
            this.button5.Size = new System.Drawing.Size(32, 24);
            this.button5.TabIndex = 67;
            this.button5.Text = "5";
            this.button5.UseVisualStyleBackColor = true;
            this.button5.Click += new System.EventHandler(this.Button5_Click);
            //
            // button6
            //
            this.button6.Location = new System.Drawing.Point(105, 117);
            this.button6.Name = "button6";
            this.button6.Size = new System.Drawing.Size(32, 24);
            this.button6.TabIndex = 68;
            this.button6.Text = "6";
            this.button6.UseVisualStyleBackColor = true;
            this.button6.Click += new System.EventHandler(this.Button6_Click);
            //
            // button7
            //
            this.button7.Location = new System.Drawing.Point(29, 87);
            this.button7.Name = "button7";
            this.button7.Size = new System.Drawing.Size(32, 24);
            this.button7.TabIndex = 69;
            this.button7.Text = "7";
            this.button7.UseVisualStyleBackColor = true;
            this.button7.Click += new System.EventHandler(this.Button7_Click);
            //
            // button8
            //
            this.button8.Location = new System.Drawing.Point(67, 87);
            this.button8.Name = "button8";
            this.button8.Size = new System.Drawing.Size(32, 24);
            this.button8.TabIndex = 70;
            this.button8.Text = "8";
            this.button8.UseVisualStyleBackColor = true;
            this.button8.Click += new System.EventHandler(this.Button8_Click);
            //
            // button9
            //
            this.button9.Location = new System.Drawing.Point(105, 87);
            this.button9.Name = "button9";
            this.button9.Size = new System.Drawing.Size(32, 24);
            this.button9.TabIndex = 71;
            this.button9.Text = "9";
            this.button9.UseVisualStyleBackColor = true;
            this.button9.Click += new System.EventHandler(this.Button9_Click);
            //
            // chkLock
            //
            this.chkLock.AutoSize = true;
            this.chkLock.Location = new System.Drawing.Point(153, 237);
            this.chkLock.Name = "chkLock";
            this.chkLock.Size = new System.Drawing.Size(62, 17);
            this.chkLock.TabIndex = 72;
            this.chkLock.Text = "Locked";
            this.chkLock.UseVisualStyleBackColor = true;
            this.chkLock.CheckedChanged += new System.EventHandler(this.chkLock_CheckedChanged);
            //
            // txtRate
            //
            this.txtRate.Location = new System.Drawing.Point(26, 240);
            this.txtRate.Name = "txtRate";
            this.txtRate.Size = new System.Drawing.Size(121, 20);
            this.txtRate.TabIndex = 73;
            this.txtRate.Leave += new System.EventHandler(this.txtRate_Leave);
            //
            // label1
            //
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(26, 224);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(81, 13);
            this.label1.TabIndex = 74;
            this.label1.Text = "Exchange Rate";
            //
            // btnBack
            //
            this.btnBack.Location = new System.Drawing.Point(26, 48);
            this.btnBack.Name = "btnBack";
            this.btnBack.Size = new System.Drawing.Size(73, 31);
            this.btnBack.TabIndex = 75;
            this.btnBack.Text = "Convert <--";
            this.btnBack.UseVisualStyleBackColor = true;
            this.btnBack.Click += new System.EventHandler(this.btnBack_Click);
            //
            // btnForward
            //
            this.btnForward.Location = new System.Drawing.Point(105, 48);
            this.btnForward.Name = "btnForward";
            this.btnForward.Size = new System.Drawing.Size(76, 31);
            this.btnForward.TabIndex = 76;
            this.btnForward.Text = "Convert -->";
            this.btnForward.UseVisualStyleBackColor = true;
            this.btnForward.Click += new System.EventHandler(this.btnForward_Click);
            //
            // btnClear
            //
            this.btnClear.Location = new System.Drawing.Point(143, 157);
            this.btnClear.Name = "btnClear";
            this.btnClear.Size = new System.Drawing.Size(38, 48);
            this.btnClear.TabIndex = 77;
            this.btnClear.Text = "C";
            this.btnClear.UseVisualStyleBackColor = true;
            //
            // btnPoint
            //
            this.btnPoint.Font = new System.Drawing.Font("Microsoft Sans Serif", 5F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.btnPoint.Image = ((System.Drawing.Image)(resources.GetObject("btnPoint.Image")));
            this.btnPoint.Location = new System.Drawing.Point(105, 180);
            this.btnPoint.Name = "btnPoint";
            this.btnPoint.Size = new System.Drawing.Size(32, 24);
            this.btnPoint.TabIndex = 78;
            this.btnPoint.Text = ".";
            this.btnPoint.UseVisualStyleBackColor = true;
            this.btnPoint.Click += new System.EventHandler(this.btnPoint_Click);
            //
            // Form1
            //
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(218, 273);
            this.Controls.Add(this.btnPoint);
            this.Controls.Add(this.btnClear);
            this.Controls.Add(this.btnForward);
            this.Controls.Add(this.btnBack);
            this.Controls.Add(this.label1);
            this.Controls.Add(this.txtRate);
            this.Controls.Add(this.chkLock);
            this.Controls.Add(this.button9);
            this.Controls.Add(this.button8);
            this.Controls.Add(this.button7);
            this.Controls.Add(this.button6);
            this.Controls.Add(this.button5);
            this.Controls.Add(this.button4);
            this.Controls.Add(this.button3);
            this.Controls.Add(this.button2);
            this.Controls.Add(this.Button1);
            this.Controls.Add(this.Button0);
            this.Controls.Add(this.btnBackspace);
            this.Controls.Add(this.txtDisplay);
            this.Name = "Form1";
            this.Text = "Form1";
            this.Load += new System.EventHandler(this.Form1_Load);
            this.ResumeLayout(false);
            this.PerformLayout();
        }
        #endregion
        private System.Windows.Forms.TextBox txtDisplay;
        private System.Windows.Forms.Button btnBackspace;
        private System.Windows.Forms.Button Button0;
        private System.Windows.Forms.Button Button1;
        private System.Windows.Forms.Button button2;
        private System.Windows.Forms.Button button3;
        private System.Windows.Forms.Button button4;
        private System.Windows.Forms.Button button5;
        private System.Windows.Forms.Button button6;
        private System.Windows.Forms.Button button7;
        private System.Windows.Forms.Button button8;
        private System.Windows.Forms.Button button9;
        private System.Windows.Forms.CheckBox chkLock;
        private System.Windows.Forms.TextBox txtRate;
        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.Button btnBack;
        private System.Windows.Forms.Button btnForward;
        private System.Windows.Forms.Button btnClear;
        private System.Windows.Forms.Button btnPoint;
        private bool just_cleared = true;
        private double old_rate;
       
       
    }
}