SecureString.SetAt Method (System.Security)

SetAt Method

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This page is specific to

Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

SecureString..::.SetAt Method

Updated: November 2007

Replaces the existing character at the specified index position with another character.

Namespace: System.Security
Assembly: mscorlib (in mscorlib.dll)

Syntax

Visual Basic (Declaration)

Public Sub SetAt ( _
    index As Integer, _
    c As Char _
)

Visual Basic (Usage)

Dim instance As SecureString
Dim index As Integer
Dim c As Char

instance.SetAt(index, c)

public void SetAt(
    int index,
    char c
)

Visual C++

public:
void SetAt(
    int index, 
    wchar_t c
)

public void SetAt(
    int index,
    char c
)

JScript

public function SetAt(
    index : int, 
    c : char
)

Parameters

index: Type: System..::.Int32
The index position of an existing character in this secure string

c: Type: System..::.Char
A character that replaces the existing character.

Exceptions

Exception	Condition
ObjectDisposedException	This secure string has already been disposed.
InvalidOperationException	This secure string is read-only.
ArgumentOutOfRangeException	index is less than zero, or greater than or equal to the length of this secure string.
CryptographicException	An error occurred while encrypting or decrypting the value of this secure string.

Remarks

The index is zero-based and the first character in this instance is at index position zero.

The value of the secure string, if any, is decrypted; c is assigned to the specified index position; then the new value is encrypted.

Examples

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

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
*/

Visual 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
*/

Platforms

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0

Reference

SecureString Class

SecureString Members

System.Security Namespace

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