SecureString.Clear Method

Reference

Definition

Namespace:: System.Security

Assembly:: System.Runtime.InteropServices.dll

Assembly:: System.Security.SecureString.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: SecureString.cs

Source:: SecureString.cs

Source:: SecureString.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Deletes the value of the current secure string.

public:
 void Clear();

public void Clear ();

member this.Clear : unit -> unit

Public Sub Clear ()

Exceptions

ObjectDisposedException

This secure string has already been disposed.

InvalidOperationException

This secure string is read-only.

Examples

The following example demonstrates how the AppendChar, InsertAt, RemoveAt, SetAt, and Clear methods affect the value of a SecureString object.

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

Remarks

The computer memory that contains the value of this secure string is zeroed, then the length of the value of this secure string is set to zero.

Applies to

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