SecureString.AppendChar(Char) 方法

定义

命名空间:

System.Security

程序集:

System.Runtime.InteropServices.dll

Source:

SecureString.cs

在当前安全字符串的末尾追加一个字符。

public:
 void AppendChar(char c);

public void AppendChar (char c);

member this.AppendChar : char -> unit

Public Sub AppendChar (c As Char)

参数

c

Char

要追加到此安全字符串的字符。

例外

ObjectDisposedException

已处置此安全字符串。

InvalidOperationException

此安全字符串是只读的。

ArgumentOutOfRangeException

执行此操作将使此安全字符串的长度超过 65,536 个字符。

CryptographicException

保护或取消保护此安全字符串的值时出错。

示例

以下示例演示 、AppendChar、、 SetAtRemoveAt和 Clear 方法如何影响 对象的值SecureString。 InsertAt

using namespace System;
using namespace System::Security;

void main()
{
    String^ msg = L"   The current length of the SecureString object: {0}\n";
    SecureString ^ ss = gcnew SecureString;

    Console::WriteLine(L"1) Instantiate the SecureString object:");
    Console::WriteLine(msg, ss->Length );

    Console::WriteLine(L"2) Append 'a' to the value:");
    ss->AppendChar('a');
    Console::WriteLine(msg, ss->Length );

    Console::WriteLine(L"3) Append 'X' to the value:");
    ss->AppendChar('X');
    Console::WriteLine(msg, ss->Length);

    Console::WriteLine(L"4) Append 'c' to the value:");
    ss->AppendChar('c');
    Console::WriteLine(msg, ss->Length);

    Console::WriteLine(L"5) Insert 'd' at the end of the value:");
    ss->InsertAt(ss->Length, 'd');
    Console::WriteLine(msg, ss->Length);

    Console::WriteLine(L"6) Remove the last character ('d') from the value:");
    ss->RemoveAt(3);
    Console::WriteLine(msg, ss->Length);

    Console::WriteLine(L"7) Set the second character ('X') of the value to 'b':" );
    ss->SetAt(1, 'b');
    Console::WriteLine(msg, ss->Length );

    Console::WriteLine(L"8) Delete the value of the SecureString object:");
    ss->Clear();
    Console::WriteLine(msg, ss->Length);

    delete ss;
}

/*
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
*/

using System;
using System.Security;

class Example
{
    public static void Main()
    {
       string msg = "The curent length of the SecureString object: {0}\n";
       Console.WriteLine("1) Instantiate the SecureString object.");
       SecureString ss = new SecureString();
       Console.WriteLine(msg, ss.Length);

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

       Console.WriteLine("3) Append 'X' to the value.");
       ss.AppendChar('X');
       Console.WriteLine(msg, ss.Length);

       Console.WriteLine("4) Append 'c' to the value.");
       ss.AppendChar('c');
       Console.WriteLine(msg, ss.Length);

       Console.WriteLine("5) Insert 'd' at the end of the value.");
       ss.InsertAt(ss.Length, 'd');
       Console.WriteLine(msg, ss.Length);

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

       Console.WriteLine("7) Set the second character of the value to 'b'.");
       ss.SetAt(1, 'b');
       Console.WriteLine(msg, ss.Length);

       Console.WriteLine("8) Delete the value of the SecureString object:");
       ss.Clear();
       Console.WriteLine(msg, ss.Length);

       ss.Dispose();
    }
}
// The example displays the following output:
//       1) Instantiate the SecureString object.
//       The curent length of the SecureString object: 0
//
//       2) Append 'a' to the value.
//       The curent length of the SecureString object: 1
//
//       3) Append 'X' to the value.
//       The curent length of the SecureString object: 2
//
//       4) Append 'c' to the value.
//       The curent length of the SecureString object: 3
//
//       5) Insert 'd' at the end of the value.
//       The curent length of the SecureString object: 4
//
//       6) Remove the last character ('d') from the value.
//       The curent length of the SecureString object: 3
//
//       7) Set the second character of the value to 'b'.
//       The curent length of the SecureString object: 3
//
//       8) Delete the value of the SecureString object:
//       The curent length of the SecureString object: 0

Imports System.Security

Module Example
    Public Sub Main()
       Dim msg As String = "The curent length of the SecureString object: {0}" + vbCrLf
       Console.WriteLine("1) Instantiate the SecureString object.")
       Dim ss As New SecureString()
       Console.WriteLine(msg, ss.Length)

       Console.WriteLine("2) Append 'a' to the value.")
       ss.AppendChar("a"c)
       Console.WriteLine(msg, ss.Length)

       Console.WriteLine("3) Append 'X' to the value.")
       ss.AppendChar("X"c)
       Console.WriteLine(msg, ss.Length)

       Console.WriteLine("4) Append 'c' to the value.")
       ss.AppendChar("c"c)
       Console.WriteLine(msg, ss.Length)

       Console.WriteLine("5) Insert 'd' at the end of the value.")
       ss.InsertAt(ss.Length, "d"c)
       Console.WriteLine(msg, ss.Length)

       Console.WriteLine("6) Remove the last character ('d') from the value.")
       ss.RemoveAt(3)
       Console.WriteLine(msg, ss.Length)

       Console.WriteLine("7) Set the second character of the value to 'b'.")
       ss.SetAt(1, "b"c)
       Console.WriteLine(msg, ss.Length)

       Console.WriteLine("8) Delete the value of the SecureString object:")
       ss.Clear()
       Console.WriteLine(msg, ss.Length)

       ss.Dispose()
    End Sub
End Module
' The example displays the following output:
'       1) Instantiate the SecureString object.
'       The curent length of the SecureString object: 0
'
'       2) Append 'a' to the value.
'       The curent length of the SecureString object: 1
'
'       3) Append 'X' to the value.
'       The curent length of the SecureString object: 2
'
'       4) Append 'c' to the value.
'       The curent length of the SecureString object: 3
'
'       5) Insert 'd' at the end of the value.
'       The curent length of the SecureString object: 4
'
'       6) Remove the last character ('d') from the value.
'       The curent length of the SecureString object: 3
'
'       7) Set the second character of the value to 'b'.
'       The curent length of the SecureString object: 3
'
'       8) Delete the value of the SecureString object:
'       The curent length of the SecureString object: 0

以下示例演示如何 AppendChar 使用 和 RemoveAt 方法收集密码中的字符。

using namespace System;
using namespace System::Security;

void main()
{
   bool go = true;
   ConsoleKeyInfo cki;
   String^ m = L"\nEnter your password (up to 15 letters, numbers, and underscores)\n"
               L"Press BACKSPACE to delete the last character entered. " +
               L"\nPress Enter when done, or ESCAPE to quit:";
   SecureString ^ password = gcnew SecureString;
   int top;
   int left;
   
   // The Console.TreatControlCAsInput property prevents CTRL+C from
   // ending this example.
   Console::TreatControlCAsInput = true;

   Console::Clear();
   Console::WriteLine(m);
   
   top = Console::CursorTop;
   left = Console::CursorLeft;

   do {
      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("*");
         }
      }
   } while (cki.Key != ConsoleKey::Enter & password->Length < 15);

   // Make the password read-only to prevent modification.
   password->MakeReadOnly();
   // Dispose of the SecureString instance.
   delete password;

}
// The example displays output like the following:
//    Enter your password (up to 15 letters, numbers, and underscores)
//    Press BACKSPACE to delete the last character entered.
//    Press Enter when done, or ESCAPE to quit:
//    ************

using System;
using System.Security;

class Example
{
   public static void Main()
   {
      ConsoleKeyInfo cki;
      String m = "\nEnter your password (up to 15 letters, numbers, and underscores)\n" +
                 "Press BACKSPACE to delete the last character entered. " +
                 "\nPress Enter when done, or ESCAPE to quit:";
      SecureString password = new SecureString();
      int top, left;

      // The Console.TreatControlCAsInput property prevents CTRL+C from
      // ending this example.
      Console.TreatControlCAsInput = true;

      Console.Clear();
      Console.WriteLine(m);

      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.

      do {
         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('*');
            }
         }
      } while (cki.Key != ConsoleKey.Enter & password.Length < 15);

      // Make the password read-only to prevent modification.
      password.MakeReadOnly();
      // Dispose of the SecureString instance.
      password.Dispose();
   }
}
// This example displays output like the following:
//    Enter your password (up to 15 letters, numbers, and underscores)
//    Press BACKSPACE to delete the last character entered.
//    Press Enter when done, or ESCAPE to quit:
//    ************

Imports System.Security

Class Example
   Public Shared Sub Main()
      Dim cki As ConsoleKeyInfo
      Dim m As String = vbCrLf & "Enter your password (up to 15 letters, numbers, and underscores)" &
                        vbCrLf & "Press BACKSPACE to delete the last character entered. " & vbCrLf &
                        "Press Enter when done, or ESCAPE to quit: "
      Dim password As New SecureString()
      Dim top, left As Integer

      ' The Console.TreatControlCAsInput property prevents CTRL+C from
      ' ending this example.
      Console.TreatControlCAsInput = True

      Console.Clear()
      Console.WriteLine(m)

      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.
      
      Do
         cki = Console.ReadKey(True)
         If cki.Key = ConsoleKey.Escape Then Exit Do

         If cki.Key = ConsoleKey.Backspace Then
            If password.Length > 0 Then
               Console.SetCursorPosition(left + password.Length - 1, top)
               Console.Write(" "c)
               Console.SetCursorPosition(left + password.Length - 1, top)
               password.RemoveAt(password.Length - 1)
            End If
         Else
            If password.Length < 15 AndAlso([Char].IsLetterOrDigit(cki.KeyChar) _
            OrElse cki.KeyChar = "_"c) Then
               password.AppendChar(cki.KeyChar)
               Console.SetCursorPosition(left + password.Length - 1, top)
               Console.Write("*"c)
            End If
         End If
      Loop While cki.Key <> ConsoleKey.Enter And password.Length < 15

      ' Make the password read-only to prevent modification.
      password.MakeReadOnly()
      ' Dispose of the SecureString instance.
      password.Dispose()
   End Sub
End Class
' The example displays output like the following:
'    Enter your password (up to 15 letters, numbers, and underscores)
'    Press BACKSPACE to delete the last character entered.
'    Press Enter when done, or ESCAPE to quit:
'    ************

注解

如果实现使用保护机制（例如加密），则此安全字符串的值（如果有）不受保护; c 追加;然后重新保护安全字符串的新值。