Find Area of Rectangle, Triangle and Circle in C#

This is a simple C# program code to find area of a rectangle, circle and triangle with user interface and example.

Manually we can find the area of a rectangle by using equation: 

Area = Breadth * Length. 

Also we can find the area of a circle by using equation: 

Area = 3.14 * (radius)²

Also we can find the area of a triangle by using equation: 
a = length of first side 
b = length of second side 
c = length of third side 
s = (a + b+ c)/2 

Area = sqrt(s*(s-a)*(s-b)*(s-c))

-where sqrt stands for square root 

User interface with example: 

Here ‘Find Area’ is the ‘button_1’. There are three tabs: One is for ‘Rectangle’, another one is for ‘Triangle’ and last is for ‘Circle’.

Code Behind interface: 

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

        private void button1_Click(object sender, EventArgs e)
        {
            if (tabControl1.SelectedTab == tabPage1)
            {
                double breadth = Convert.ToDouble(textBox1.Text);
                double lenght = Convert.ToDouble(textBox2.Text);
                label5.Text = (breadth * lenght).ToString();
            }
            if (tabControl1.SelectedTab == tabPage2)
            {
                double a = Convert.ToDouble(textBox4.Text);
                double b = Convert.ToDouble(textBox5.Text);
                double c = Convert.ToDouble(textBox6.Text);
                double s = (a + b + c) / 2;
                double Area = Math.Sqrt(s * (s - a) * (s - b) * (s - c));
                label5.Text = (Area).ToString();
            }
            if (tabControl1.SelectedTab == tabPage3)
            {
                double  radius = Convert.ToDouble(textBox3.Text);
                label5.Text = (3.14 * radius).ToString();
            }
        }
    }
}

Mroe C# programs are here