Text Changed Event

 

namespace Zau_TextChangedEvent
{

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

        private void Form1_Load(object sender, EventArgs e)
        {
            //display all textboxes
            textBox1.Enabled = false;
            textBox2.Enabled = false;
            textBox3.Enabled = false;
            textBox4.Enabled = false;
            textBox5.Enabled = false;
            textBox6.Enabled = false;
        }

        private void checkBox1_CheckedChanged(object sender, EventArgs e)
        {
            if (checkBox1.Checked)
            {
                textBox1.Enabled = true;
                textBox4.Enabled = true;
            }
            else
            {
                textBox1.Enabled = false;
                textBox4.Enabled = false;
                textBox1.Clear();
                textBox4.Clear();
            }
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            int q;
            int.TryParse(textBox1.Text, out q);
            decimal subt1 = q * 4.99m;
            textBox4.Text = subt1.ToString("c");
        }
    }
}