SecureString.RemoveAt(Int32) 方法
定义
重要
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从此安全字符串中的指定索引位置移除字符。
public:
void RemoveAt(int index);public void RemoveAt (int index);[System.Runtime.ExceptionServices.HandleProcessCorruptedStateExceptions]
public void RemoveAt (int index);member this.RemoveAt : int -> unit[<System.Runtime.ExceptionServices.HandleProcessCorruptedStateExceptions>]
member this.RemoveAt : int -> unitPublic Sub RemoveAt (index As Integer)参数
- index
- Int32
此安全字符串中的字符的索引位置。
- 属性
例外
已处置此安全字符串。
此安全字符串是只读的。
index 小于零，或者大于或等于此安全字符串的长度。
保护或取消保护此安全字符串的值时出错。
示例
下面的示例演示 、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 SecureStringExample
{
public static void Main()
{
string msg = "The current 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 current length of the SecureString object: 0
//
// 2) Append 'a' to the value.
// The current length of the SecureString object: 1
//
// 3) Append 'X' to the value.
// The current length of the SecureString object: 2
//
// 4) Append 'c' to the value.
// The current length of the SecureString object: 3
//
// 5) Insert 'd' at the end of the value.
// The current length of the SecureString object: 4
//
// 6) Remove the last character ('d') from the value.
// The current length of the SecureString object: 3
//
// 7) Set the second character of the value to 'b'.
// The current length of the SecureString object: 3
//
// 8) Delete the value of the SecureString object:
// The current length of the SecureString object: 0
Imports System.Security
Module Example
Public Sub Main()
Dim msg As String = "The current 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 current length of the SecureString object: 0
'
' 2) Append 'a' to the value.
' The current length of the SecureString object: 1
'
' 3) Append 'X' to the value.
' The current length of the SecureString object: 2
'
' 4) Append 'c' to the value.
' The current length of the SecureString object: 3
'
' 5) Insert 'd' at the end of the value.
' The current length of the SecureString object: 4
'
' 6) Remove the last character ('d') from the value.
' The current length of the SecureString object: 3
'
' 7) Set the second character of the value to 'b'.
' The current length of the SecureString object: 3
'
' 8) Delete the value of the SecureString object:
' The current 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
索引从零开始;此实例中的第一个字符位于索引位置 0。
如果实现使用加密等保护机制，则此安全字符串的值（如果有）将不受保护;删除指定索引位置处的字符;则重新保护新值。
