SecureString.Clear 方法
定義
重要
部分資訊涉及發行前產品,在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊,不做任何明確或隱含的瑕疵擔保。
刪除目前安全字串的值。
public:
void Clear();
public void Clear ();
member this.Clear : unit -> unit
Public Sub Clear ()
例外狀況
這個安全字串已經過處置。
這個安全字串是唯讀的。
範例
下列範例示範 、、、 和 方法如何影響 AppendChar物件的值。RemoveAtClearSetAtInsertAtSecureString
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
備註
包含此安全字串值的計算機記憶體為零,則這個安全字串串的值長度會設定為零。
適用於
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