SecureString.MakeReadOnly 方法
定义
将此安全字符串的文本值设置为只读。Makes the text value of this secure string read-only.
public:
void MakeReadOnly();
public void MakeReadOnly ();
member this.MakeReadOnly : unit -> unit
Public Sub MakeReadOnly ()
例外
已处置此安全字符串。This secure string has already been disposed.
示例
下面的示例演示如何 AppendChar 使用和 RemoveAt 方法收集密码中的字符。The following example demonstrates how the AppendChar and RemoveAt methods can be used to collect the characters in a password. 密码在收集后变为只读。After the password is collected, it is made read-only.
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
使用构造函数初始化类的实例的文本值 SecureString SecureString ,并使用 Clear 、 RemoveAt 、、 SetAt InsertAt 和 AppendChar 方法修改该值。Initialize the text value of an instance of the SecureString class with the SecureString constructors, and modify the value with the Clear, RemoveAt, SetAt, InsertAt, and AppendChar methods.
进行最终修改后,使用方法将实例的 MakeReadOnly 值变为不可变 (只读) 。After you have made your final modifications, use the MakeReadOnly method to make the value of the instance immutable (read-only). 将该值标记为只读后,对其进行修改的任何进一步尝试都将引发 InvalidOperationException 。After the value is marked as read-only, any further attempt to modify it throws an InvalidOperationException.
调用的效果 MakeReadOnly 是永久性的,因为 SecureString 类不提供任何方法来使安全字符串再次被修改。The effect of invoking MakeReadOnly is permanent because the SecureString class provides no means to make the secure string modifiable again. 使用 IsReadOnly 方法来测试实例是否 SecureString 为只读的。Use the IsReadOnly method to test whether an instance of SecureString is read-only.