SecureString.RemoveAt メソッドとは何？わかりやすく解説 Weblio辞書

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.NET Framework クラスライブラリリファレンス

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SecureString.RemoveAt メソッド

メモ : このメソッドは、.NET Framework version 2.0 で新しく追加されたものです。

このセキュリティ文字列の指定されたインデックス位置にある文字を削除します。

名前空間: System.Security
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Sub RemoveAt ( _
    index As Integer _
)

Visual Basic (使用法)

Dim instance As SecureString
Dim index As Integer

instance.RemoveAt(index)

public void RemoveAt (
    int index
)

C++

public:
void RemoveAt (
    int index
)

public void RemoveAt (
    int index
)

JScript

public function RemoveAt (
    index : int
)

パラメータ

index: このセキュリティ文字列に含まれる文字のインデックス位置。

例外

例外の種類	条件
ObjectDisposedException	このセキュリティ文字列は、既に破棄されています。
InvalidOperationException	このセキュリティ文字列は読み取り専用です。
ArgumentOutOfRangeException	index が、0 未満か、このセキュリティ文字列の長さ以上です。
CryptographicException	このセキュリティ文字列の値を暗号化または復号化するときにエラーが発生しました。

解説

インデックスは 0 から始まり、このインスタンスの最初の文字がインデックス位置 0 になります。

このセキュリティ文字列の値が存在する場合、その値が復号化され、指定されたインデックス位置の文字が削除されます。その後、新しい値が暗号化されます。

使用例

AppendChar、InsertAt、RemoveAt、SetAt、Clear の各メソッドが SecureString オブジェクトの値にどのような影響を与えるかをデモンストレーションするコード例を次に示します。

Visual Basic

' This example demonstrates the AppendChar, 
' InsertAt, RemoveAt, SetAt, and Clear methods.
Imports System
Imports System.Security

Class Sample
   Public Shared Sub Main()
      Dim msg1 As String
 = "   SecureString = {0}" & vbCrLf & "
   Length = {1}" & vbCrLf
      Dim msg2 As String
 = "This example demonstrates the effect of the AppendChar, InsertAt,"
 & vbCrLf & _
                           "RemoveAt, SetAt, and Clear methods
 on the value of a SecureString" & vbCrLf & _
                           "object. This example simulates the
 value of the object because the" & vbCrLf & _
                           "actual value is encrypted."
 & vbCrLf
      Dim ss As New SecureString()
' 
'  This sample modifies the contents of a SecureString, ss, in
'  several steps. After each step, the length and simulated value of
 ss 
'  are displayed. The actual value of ss is encrypted.
'
      Console.WriteLine(msg2)
      
      Console.WriteLine("1) The initial value of the SecureString
 object:")
      Console.WriteLine(msg1, """""",
 ss.Length)
      
      Console.WriteLine("2) AppendChar: Append 'a' to the value:")
      ss.AppendChar("a"c)
      Console.WriteLine(msg1, """a""",
 ss.Length)
      
      Console.WriteLine("3) AppendChar: Append 'X' to the value:")
      ss.AppendChar("X"c)
      Console.WriteLine(msg1, """aX""",
 ss.Length)
      
      Console.WriteLine("4) AppendChar: Append 'c' to the value:")
      ss.AppendChar("c"c)
      Console.WriteLine(msg1, """aXc""",
 ss.Length)
      
      Console.WriteLine(("5) InsertAt: Insert 'd' at the end of
 the value (equivalent" & vbCrLf & "     to AppendChar):"))
      ss.InsertAt(ss.Length, "d"c)
      Console.WriteLine(msg1, """aXcd""",
 ss.Length)
      
      Console.WriteLine("6) RemoveAt: Remove the last character ('d')
 from the value:")
      ss.RemoveAt(3)
      Console.WriteLine(msg1, """aXc""",
 ss.Length)
      
      Console.WriteLine("7) SetAt: Set the second character
 ('X') of the value to 'b':")
      ss.SetAt(1, "b"c)
      Console.WriteLine(msg1, """abc""",
 ss.Length)
      
      Console.WriteLine("8) Clear: Delete the value of the SecureString
 object:")
      ss.Clear()
      Console.WriteLine(msg1, """""",
 ss.Length)
   End Sub 'Main
End Class 'Sample
'
'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
'

// This example demonstrates the AppendChar, 
// InsertAt, RemoveAt, SetAt, and Clear methods.

using System;
using System.Security;

class Sample 
{
    public static void Main()
 
    {
    string msg1 = "   SecureString = {0}\n   Length = {1}\n";
    string msg2 = "This example demonstrates the effect of
 the AppendChar, InsertAt,\n" +
                  "RemoveAt, SetAt, and Clear methods on the value of a SecureString\n"
 +
                  "object. This example simulates the value of the object because
 the\n" +
                  "actual value is encrypted.\n";
    SecureString ss = new SecureString();
/* 
  This sample modifies the contents of a SecureString, ss, in
  several steps. After each step, the length and simulated value of ss 
  are displayed. The actual value of ss is encrypted.
*/
    Console.WriteLine(msg2);

    Console.WriteLine("1) The initial value of the SecureString object:");
    Console.WriteLine(msg1, "\"\"", ss.Length);

    Console.WriteLine("2) AppendChar: Append 'a' to the value:");
    ss.AppendChar('a');
    Console.WriteLine(msg1, "\"a\"", ss.Length);

    Console.WriteLine("3) AppendChar: Append 'X' to the value:");
    ss.AppendChar('X');
    Console.WriteLine(msg1, "\"aX\"", ss.Length);

    Console.WriteLine("4) AppendChar: Append 'c' to the value:");
    ss.AppendChar('c');
    Console.WriteLine(msg1, "\"aXc\"", ss.Length);

    Console.WriteLine("5) InsertAt: Insert 'd' at the end of the value (equivalent\n"
 +
                      "     to AppendChar):");
    ss.InsertAt(ss.Length, 'd');
    Console.WriteLine(msg1, "\"aXcd\"", ss.Length);

    Console.WriteLine("6) RemoveAt: Remove the last character ('d') from the
 value:");
    ss.RemoveAt(3);
    Console.WriteLine(msg1, "\"aXc\"", ss.Length);

    Console.WriteLine("7) SetAt: Set the second character ('X') of the value
 to 'b':");
    ss.SetAt(1, 'b');
    Console.WriteLine(msg1, "\"abc\"", ss.Length);

    Console.WriteLine("8) Clear: Delete the value of the SecureString object:");
    ss.Clear();
    Console.WriteLine(msg1, "\"\"", ss.Length);
    }
}
/*
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
*/

C++

// This example demonstrates the AppendChar,
// InsertAt, RemoveAt, SetAt, and Clear methods.

using namespace System;
using namespace System::Security;

int main()
{
    String^ msg1 = L"   SecureString = {0}\n   Length = {1}\n";
    String^ msg2 = L"This example demonstrates the effect of the AppendChar,
 InsertAt,\n"
    L"RemoveAt, SetAt, and Clear methods on the value of a SecureString\n"
    L"object. This example simulates the value of the object because the\n"
    L"actual value is encrypted.\n";
    SecureString ^ ss = gcnew SecureString;

    // This sample modifies the contents of a SecureString, ss, in
    // several steps. After each step, the length and simulated value
 of ss
    // are displayed. The actual value of ss is encrypted.
    Console::WriteLine( msg2 );
    Console::WriteLine( L"1) The initial value of the SecureString object:"
 );
    Console::WriteLine( msg1, L"\"\"", ss->Length );
    Console::WriteLine( L"2) AppendChar: Append 'a' to the value:" );

    ss->AppendChar( 'a' );
    Console::WriteLine( msg1, L"\"a\"", ss->Length );
    Console::WriteLine( L"3) AppendChar: Append 'X' to the value:" );

    ss->AppendChar( 'X' );
    Console::WriteLine( msg1, L"\"aX\"", ss->Length );
    Console::WriteLine( L"4) AppendChar: Append 'c' to the value:" );

    ss->AppendChar( 'c' );
    Console::WriteLine( msg1, L"\"aXc\"", ss->Length );
    Console::WriteLine( L"5) InsertAt: Insert 'd' at the end of the value (equivalent\n"
                        L"     to AppendChar):" );

    ss->InsertAt( ss->Length, 'd' );
    Console::WriteLine( msg1, L"\"aXcd\"", ss->Length );
    Console::WriteLine( L"6) RemoveAt: Remove the last character ('d') from
 the value:" );

    ss->RemoveAt( 3 );
    Console::WriteLine( msg1, L"\"aXc\"", ss->Length );
    Console::WriteLine( L"7) SetAt: Set the second character ('X') of the value
 to 'b':" );

    ss->SetAt( 1, 'b' );
    Console::WriteLine( msg1, L"\"abc\"", ss->Length );
    Console::WriteLine( L"8) Clear: Delete the value of the SecureString object:"
 );

    ss->Clear();
    Console::WriteLine( msg1, L"\"\"", ss->Length );

    return 0;
}

/*
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
*/

AppendChar メソッドおよび RemoveAt メソッドを使用してパスワード内の文字を収集する方法を次のコード例に示します。

Visual Basic

' This example demonstrates using the AppendChar and RemoveAt 
' methods to collect a password.

Imports System
Imports System.Security

Class Sample
   Public Shared Sub Main()
      Dim cki As ConsoleKeyInfo
      Dim m1 As String =
 "(This example simulates entering a password. "
 & _
                         "Do not enter an actual password.)"
 & vbCrLf
      Dim m2 As String =
 "Enter your password (up to 15 letters, numbers, and underscores)"
 & vbCrLf & "Press BACKSPACE to delete the last character entered. " & vbCrLf & _
                         "Press ESCAPE to quit:"
      Dim password As New
 SecureString()
      Dim top, left As Integer
      '
      ' The Console.TreatControlCAsInput property prevents this example
 from
      ' ending if you press CTL+C, however all other operating system
 keys and 
      ' shortcuts, such as ALT+TAB or the Windows Logo key, are still
 in effect. 
      ' Each input character is assumed to occupy one screen column.
      '
      Console.TreatControlCAsInput = True

      Console.Clear()
      Console.WriteLine(m1)
      Console.WriteLine(m2)

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

      ' Make the password read-only to prevent it from being modified
 after it has 
      ' been collected. 

      password.MakeReadOnly()
   End Sub 'Main
End Class 'Sample
'
'This example produces results similar to the following text:
'
'(This example simulates entering a password. Do not enter an actual
 password.)
'
'Enter your password (up to 15 letters, numbers, and underscores)
'Press BACKSPACE to delete the last character entered.
'Press ESCAPE to quit:
'***************
'

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0

参照

関連項目
SecureString クラス
SecureString メンバ
System.Security 名前空間

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SecureString.RemoveAt メソッドとは？ わかりやすく解説

SecureString.RemoveAt メソッド

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SecureString.RemoveAt メソッドとは？わかりやすく解説