my code is:
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 WindowsFormsApplication2
{
public partial class Form1 : Form
{
double num;
string text = "";
public Form1()
{
InitializeComponent();
}
private void calFactorial_TextChanged(object sender, EventArgs e)
{
if (calFactorial.Text != "")
{
if (!(Char.IsNumber(calFactorial.Text, 0)))
{
factLabel.Text = "Enter number only";
}
else if (Convert.ToDouble(calFactorial.Text) == 0)
{
factLabel.Text = "Please provide a Number greater than 0.";
}
}
else
{
factLabel.Text = "Please Enter Number";
}
}
private void factorial_Click(object sender, EventArgs e)
{
if (calFactorial.Text == "")
{
factLabel.Text = "Please enter a number";
}
else
{
num = Convert.ToDouble(calFactorial.Text);
RichTextBox richTextBox = new RichTextBox();
foreach (Control removeControl in Controls)
{
removeControl.Hide();
calFactorial.Show();
factLabel.Show();
factorial.Show();
}
Button clear = new Button();
clear.Location = new Point(500, 150);
richTextBox.Location = new Point(100, 100);
richTextBox.Size = new Size(300, 200);
clear.Text = "Clear";
this.Controls.Add(clear);
this.Controls.Add(richTextBox);
double fact = 1;
for (double i = num; i >= 1; i--)
{
fact = fact * i;
}
richTextBox.Text = text + "The factorial of " + Convert.ToString(num) + " is: " + Convert.ToString(fact) + "\n";
text = richTextBox.Text;
clear.Click += new EventHandler(ClearClick);
richTextBox.TextChanged += new EventHandler(ClearClick);
}
}
private void ClearClick(object sender, EventArgs e)
{
foreach (Control removeControl in Controls)
{
removeControl.Hide();
calFactorial.Show();
factLabel.Show();
factorial.Show();
calFactorial.Text = "";
}
}
}
}