SecureString.MakeReadOnly Metoda
Definice
Důležité
Některé informace platí pro předběžně vydaný produkt, který se může zásadně změnit, než ho výrobce nebo autor vydá. Microsoft neposkytuje žádné záruky, výslovné ani předpokládané, týkající se zde uváděných informací.
Nastaví textovou hodnotu tohoto zabezpečeného řetězce jen pro čtení.
public:
void MakeReadOnly();
public void MakeReadOnly ();
member this.MakeReadOnly : unit -> unit
Public Sub MakeReadOnly ()
Výjimky
Tento zabezpečený řetězec již byl uvolněn.
Příklady
Následující příklad ukazuje, jak AppendChar RemoveAt lze metody a použít ke shromáždění znaků v hesle. Po shromáždění hesla bude provedeno jen pro čtení.
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:
' ************
Poznámky
Inicializujte textovou hodnotu instance SecureString třídy s SecureString konstruktory a upravte hodnotu pomocí Clear RemoveAt metod,, SetAt , InsertAt a AppendChar .
Až provedete poslední změny, použijte MakeReadOnly metodu pro nastavení hodnoty neměnné instance (jen pro čtení). Jakmile je hodnota označena jako jen pro čtení, další pokus o jejich změnu vyvolá InvalidOperationException .
Účinek vyvolání MakeReadOnly je trvalý, protože SecureString Třída neposkytuje žádný způsob, jak změnit zabezpečený řetězec. Použijte IsReadOnly metodu k otestování, zda je instance SecureString určena jen pro čtení.