SecureString.Clear Método

Definición

Espacio de nombres:

System.Security

Ensamblado:

System.Runtime.InteropServices.dll

Source:

SecureString.cs

Elimina el valor de la cadena segura actual.

public:
 void Clear();

public void Clear ();

member this.Clear : unit -> unit

Public Sub Clear ()

Excepciones

ObjectDisposedException

Esta cadena segura ya se ha desechado.

InvalidOperationException

Esta cadena segura es de sólo lectura.

Ejemplos

En el ejemplo siguiente se muestra cómo los AppendCharmétodos , InsertAtRemoveAt, SetAt, y Clear afectan al valor de un SecureString objeto .

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

Comentarios

La memoria del equipo que contiene el valor de esta cadena segura está cero y, a continuación, la longitud del valor de esta cadena segura se establece en cero.

Consulte también

• Length