using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace _0604_pwdtxb
{
public class PasswordTextBox : TextBox
{
private readonly Timer timer;
private Char[] adminPassword = new Char[16];
private readonly char DecimalSeparator = CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator.ToCharArray()[0];
/// <summary>
///
/// </summary>
public PasswordTextBox()
{
timer = new Timer { Interval = 200 };
timer.Tick += timer_Tick;
}
/// <summary>
///
/// </summary>
public string AdminPassword
{
get
{
return new string(adminPassword).Trim('\0').Replace("\0", "");
}
}
/// <summary>
///
/// </summary>
/// <param name="e"></param>
protected override void OnTextChanged(EventArgs e)
{
base.OnTextChanged(e);
txtInput_TextChanged(this, e);
}
/// <summary>
///
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void txtInput_TextChanged(object sender, EventArgs e)
{
HidePasswordCharacters();
}
/// <summary>
///
/// </summary>
private void HidePasswordCharacters()
{
int index = this.SelectionStart;
if (index > 1)
{
StringBuilder s = new StringBuilder(this.Text);
s[index - 2] = '*';
this.Text = s.ToString();
this.SelectionStart = index;
}
timer.Enabled = true;
}
protected override void OnKeyDown(KeyEventArgs e)
{
base.OnKeyDown(e);
if (e.KeyCode == Keys.Delete)
{
DeleteSelectedCharacters(this, e.KeyCode);
}
}
/// <summary>
/// Windows Timer elapsed eventhandler
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void timer_Tick(object sender, EventArgs e)
{
timer.Enabled = false;
int index = this.SelectionStart;
if (index > 0)
{
StringBuilder s = new StringBuilder(this.Text);
s[index-1] = '*';
this.Invoke(new Action(() =>
{
this.Text = s.ToString();
this.SelectionStart = index;
}));
}
}
protected override void OnKeyPress(KeyPressEventArgs e)
{
base.OnKeyPress(e);
int selectionStart = this.SelectionStart;
int length = this.TextLength;
int selectedChars = this.SelectionLength;
this.TextChanged -= new System.EventHandler(txtInput_TextChanged);
if (selectedChars == length)
{
/*
* Means complete text selected so clear it before using it
*/
ClearCharBufferPlusTextBox();
}
Keys eModified = (Keys)e.KeyChar;
if (e.KeyChar == DecimalSeparator)
{
e.Handled = true;
}
if ((Keys.Delete != eModified) && (Keys.Back != eModified))
{
if (Keys.Space != eModified)
{
if (e.KeyChar != '-')
{
if (!char.IsLetterOrDigit(e.KeyChar))
{
e.Handled = true;
}
else
{
adminPassword = new string(adminPassword).Insert(selectionStart, e.KeyChar.ToString()).ToCharArray();
}
}
}
else
{
if (this.TextLength == 0)
{
e.Handled = true;
Array.Clear(adminPassword, 0, adminPassword.Length);
}
}
}
else if ((Keys.Back == eModified) || (Keys.Delete == eModified))
{
DeleteSelectedCharacters(this, eModified);
}
/*
* Replace the characters with '*'
*/
HidePasswordCharacters();
this.TextChanged += new System.EventHandler(this.txtInput_TextChanged);
}
/// <summary>
/// Deletes the specific characters in the char array based on the key press action
/// </summary>
/// <param name="sender"></param>
private void DeleteSelectedCharacters(object sender, Keys key)
{
int selectionStart = this.SelectionStart;
int length = this.TextLength;
int selectedChars = this.SelectionLength;
if (selectedChars == length)
{
ClearCharBufferPlusTextBox();
this.TextChanged += new System.EventHandler(this.txtInput_TextChanged);
return;
}
if (selectedChars > 0)
{
int i = selectionStart;
this.Text.Remove(selectionStart, selectedChars);
adminPassword = new string(adminPassword).Remove(selectionStart, selectedChars).ToCharArray();
}
else
{
/*
* Basically this portion of code is to handle the condition
* when the cursor is placed at the start or in the end
*/
if (selectionStart == 0)
{
/*
* Cursor in the beginning, before the first character
* Delete the character only when Del is pressed, No action when Back key is pressed
*/
if (key == Keys.Delete)
{
adminPassword = new string(adminPassword).Remove(0, 1).ToCharArray();
}
}
else if (selectionStart > 0 && selectionStart < length)
{
/*
* Cursor position anywhere in between
* Backspace and Delete have the same effect
*/
if (key == Keys.Back || key == Keys.Delete)
{
adminPassword = new string(adminPassword).Remove(selectionStart, 1).ToCharArray();
}
}
else if (selectionStart == length)
{
/*
* Cursor at the end, after the last character
* Delete the character only when Back key is pressed, No action when Delete key is pressed
*/
if (key == Keys.Back)
{
adminPassword = new string(adminPassword).Remove(selectionStart - 1, 1).ToCharArray();
}
}
}
}
private void ClearCharBufferPlusTextBox()
{
Array.Clear(adminPassword, 0, adminPassword.Length);
this.Clear();
}
}
}
