validate textbox entered password with in the text file.

Question

How to compare text(password) that key in textbox and with that we have set in text file like notepad.When we click button in form.

How to change the text in text file in a form with two textbox.
One for user key in old password.
Another for user to key in new password and they click button.It will change the password in text file.After this it will use the new password to compare.
Tq very much.......


For question 1:

private void textBox1_TextChanged(object sender, EventArgs e)

{????

}

private void button1_Click(object sender, EventArgs e)

{?????

}

Question 2

private void textBox1_TextChanged(object sender, EventArgs e)

{????

}

private void textBox2_TextChanged(object sender, EventArgs e)

{????

}

private void button1_Click(object sender, EventArgs e)

{?????

}