Visual C# projects

the first basic project is calculator..........its simple but its necessary

so here the program......

snapshots:

code

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;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }
        Double fno, sno, result;
       
        private void btn_add_Click(object sender, EventArgs e)
        {
            int I = Controls.Count;
            for (int i = 0; i < I; i++)
            {
                if ((String)(Controls[i].Tag) == "A" && Controls[i].Text == "")
                {
                    MessageBox.Show("you have not entered values in " + Controls[i].Name, "error", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                    Controls[i].Focus();
                    return;
                }
            }
            fno = Double.Parse(txt_fno.Text);
            sno = Double.Parse(txt_sno.Text);
            result = fno + sno;
            txt_result.Text = result.ToString();
            lbl_result.Text = "Sum";
            lbl_result.Visible = true;
            txt_result.Visible = true;
        }

        private void btn_sub_Click(object sender, EventArgs e)
        {
            int I = Controls.Count;
            for (int i = 0; i < I; i++)
            {
                if ((String)(Controls[i].Tag) == "S" && Controls[i].Text == "")
                {
                    MessageBox.Show("you have not entered values in " + Controls[i].Name, "error", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                    Controls[i].Focus();
                    return;
                }
            }
            fno = Double.Parse(txt_fno.Text);
            sno = Double.Parse(txt_sno.Text);
            result = fno - sno;
            txt_result.Text = result.ToString();
            lbl_result.Text = "Subtract";
            lbl_result.Visible = true;
        }

        private void btn_mul_Click(object sender, EventArgs e)
        {
            int I = Controls.Count;
            for (int i = 0; i < I; i++)
            {
                if ((String)(Controls[i].Tag) == "M" && Controls[i].Text == "")
                {
                    MessageBox.Show("you have not entered values in " + Controls[i].Name, "error", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                    Controls[i].Focus();
                    return;
                }
            }
            fno = Double.Parse(txt_fno.Text);
            sno = Double.Parse(txt_sno.Text);
            result = fno * sno;
            txt_result.Text = result.ToString();
            lbl_result.Text = "Multiplication";
            lbl_result.Visible = true;
        }

        private void btn_div_Click(object sender, EventArgs e)
        {
            int I = Controls.Count;
            for (int i = 0; i < I; i++)
            {
                if ((String)(Controls[i].Tag) == "D" && Controls[i].Text == "")
                {
                    MessageBox.Show("you have not entered values in " + Controls[i].Name, "error", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                    Controls[i].Focus();
                    return;
                }
            }
            fno = Double.Parse(txt_fno.Text);
            sno = Double.Parse(txt_sno.Text);
            if (sno == 0)
            {
                MessageBox.Show("not allowed");
                txt_sno.Focus();
                txt_sno.SelectionStart = 0;
                txt_sno.SelectionLength = txt_sno.Text.Length;
            }
            result = fno / sno;
            txt_result.Text = result.ToString();
            lbl_result.Text = "Division";
            lbl_result.Visible = true;
        }

        private void txt_fno_TextChanged(object sender, EventArgs e)
        {
            try
            {
                fno = Double.Parse(txt_fno.Text);
            }
            catch
            {
                SendKeys.Send("{BACKSPACE}");
            }
        }

        private void txt_sno_TextChanged(object sender, EventArgs e)
        {
            try
            {
                sno = Double.Parse(txt_sno.Text);
            }
            catch
            {
                SendKeys.Send("{BACKSPACE}");
            }
        }

        private void txt_fno_Validating(object sender, CancelEventArgs e)
        {
            if (txt_fno.Text == "")
                e.Cancel = true;
        }

        private void txt_sno_Validating(object sender, CancelEventArgs e)
        {
            if (txt_sno.Text == "")
                e.Cancel = true;
        }

        private void btn_reset_Click(object sender, EventArgs e)
        {
            txt_fno.Text = "";
            txt_sno.Text = "";
            txt_result.Text = "";
            txt_fno.Focus();       
        }

        private void btn_quit_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }
    }
}