SecureString.RemoveAt Method

// This example demonstrates the AppendChar,  
// InsertAt, RemoveAt, SetAt, and Clear methods. 

using System;
using System.Security;

class Sample 
{
    public static void Main() 
    {
    string msg1 = "   SecureString = {0}\n   Length = {1}\n";
    string msg2 = "This example demonstrates the effect of the AppendChar, InsertAt,\n" +
                  "RemoveAt, SetAt, and Clear methods on the value of a SecureString\n" +
                  "object. This example simulates the value of the object because the\n" +
                  "actual value is encrypted.\n";
    SecureString ss = new SecureString();
/* 
  This sample modifies the contents of a SecureString, ss, in
  several steps. After each step, the length and simulated value of ss 
  are displayed. The actual value of ss is encrypted.
*/
    Console.WriteLine(msg2);

    Console.WriteLine("1) The initial value of the SecureString object:");
    Console.WriteLine(msg1, "\"\"", ss.Length);

    Console.WriteLine("2) AppendChar: Append 'a' to the value:");
    ss.AppendChar('a');
    Console.WriteLine(msg1, "\"a\"", ss.Length);

    Console.WriteLine("3) AppendChar: Append 'X' to the value:");
    ss.AppendChar('X');
    Console.WriteLine(msg1, "\"aX\"", ss.Length);

    Console.WriteLine("4) AppendChar: Append 'c' to the value:");
    ss.AppendChar('c');
    Console.WriteLine(msg1, "\"aXc\"", ss.Length);

    Console.WriteLine("5) InsertAt: Insert 'd' at the end of the value (equivalent\n" +
                      "     to AppendChar):");
    ss.InsertAt(ss.Length, 'd');
    Console.WriteLine(msg1, "\"aXcd\"", ss.Length);

    Console.WriteLine("6) RemoveAt: Remove the last character ('d') from the value:");
    ss.RemoveAt(3);
    Console.WriteLine(msg1, "\"aXc\"", ss.Length);

    Console.WriteLine("7) SetAt: Set the second character ('X') of the value to 'b':");
    ss.SetAt(1, 'b');
    Console.WriteLine(msg1, "\"abc\"", ss.Length);

    Console.WriteLine("8) Clear: Delete the value of the SecureString object:");
    ss.Clear();
    Console.WriteLine(msg1, "\"\"", ss.Length);
    }
}
/*
This code example produces the following results:

This example demonstrates the effect of the AppendChar, InsertAt,
RemoveAt, SetAt, and Clear methods on the value of a SecureString
object. This example simulates the value of the object because the
actual value is encrypted.

1) The initial value of the SecureString object:
   SecureString = ""
   Length = 0

2) AppendChar: Append 'a' to the value:
   SecureString = "a"
   Length = 1

3) AppendChar: Append 'X' to the value:
   SecureString = "aX"
   Length = 2

4) AppendChar: Append 'c' to the value:
   SecureString = "aXc"
   Length = 3

5) InsertAt: Insert 'd' at the end of the value (equivalent
     to AppendChar):
   SecureString = "aXcd"
   Length = 4

6) RemoveAt: Remove the last character ('d') from the value:
   SecureString = "aXc"
   Length = 3

7) SetAt: Set the second character ('X') of the value to 'b':
   SecureString = "abc"
   Length = 3

8) Clear: Delete the value of the SecureString object:
   SecureString = ""
   Length = 0
*/

// This example demonstrates using the AppendChar and RemoveAt  
// methods to collect a password. 

using System;
using System.Security;

class Sample 
{
    public static void Main() 
    {
    ConsoleKeyInfo cki;
    String m1 = "(This example simulates entering a password. " +
                "Do not enter an actual password.)\n";
    String m2 = "Enter your password (up to 15 letters, numbers, and underscores)\n" +
                "Press BACKSPACE to delete the last character entered. \nPress ESCAPE to quit:";
    SecureString password = new SecureString();
    int top, left;

// The Console.TreatControlCAsInput property prevents this example from 
// ending if you press CTL+C, however all other operating system keys and  
// shortcuts, such as ALT+TAB or the Windows Logo key, are still in effect.  
// Each input character is assumed to occupy one screen column.

    Console.TreatControlCAsInput = true;

    Console.Clear();
    Console.WriteLine(m1);
    Console.WriteLine(m2);

    top  = Console.CursorTop;
    left = Console.CursorLeft;

// Read user input from the console. Store up to 15 letter, digit, or underscore 
// characters in a SecureString object, or delete a character if the user enters  
// a backspace. Display an asterisk (*) on the console to represent each character  
// that is stored. 

    while (true)
        {
        cki = Console.ReadKey(true);
        if (cki.Key == ConsoleKey.Escape) break;
        if (cki.Key == ConsoleKey.Backspace)
            {
            if (password.Length > 0) 
                {
                Console.SetCursorPosition(left+password.Length-1, top);
                Console.Write(' ');
                Console.SetCursorPosition(left+password.Length-1, top);
                password.RemoveAt(password.Length-1);
                }
            }
        else
            {
            if ((password.Length < 15) && 
                (Char.IsLetterOrDigit(cki.KeyChar) || cki.KeyChar == '_'))
                {
                password.AppendChar(cki.KeyChar);                 
                Console.SetCursorPosition(left+password.Length-1, top);
                Console.Write('*');
                }
            }
        }

// Make the password read-only to prevent it from being modified after it has  
// been collected. 

    password.MakeReadOnly();
    }
}
/*
This example produces results similar to the following text:

(This example simulates entering a password. Do not enter an actual password.)

Enter your password (up to 15 letters, numbers, and underscores)
Press BACKSPACE to delete the last character entered.
Press ESCAPE to quit:
***************

*/