SecureString.AppendChar(Char) Method
Definition
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.
Appends a character to the end of the current secure string.
public:
void AppendChar(char c);public void AppendChar (char c);[System.Runtime.ExceptionServices.HandleProcessCorruptedStateExceptions]
public void AppendChar (char c);member this.AppendChar : char -> unit[<System.Runtime.ExceptionServices.HandleProcessCorruptedStateExceptions>]
member this.AppendChar : char -> unitPublic Sub AppendChar (c As Char)Parameters
- c
- Char
A character to append to this secure string.
- Attributes
Exceptions
This secure string has already been disposed.
This secure string is read-only.
Performing this operation would make the length of this secure string greater than 65,536 characters.
An error occurred while protecting or unprotecting the value of this secure string.
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
The following example demonstrates how the AppendChar and RemoveAt methods can be used to collect the characters in a password.
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:
' ************
Remarks
If the implementation uses a protection mechanism, such as encryption, the value of this secure string, if any, is unprotected; c is appended; then the new value of the secure string is re-protected.
Applies to
Collaborate with us on GitHub
The source for this content can be found on GitHub, where you can also create and review issues and pull requests. For more information, see our contributor guide.
