SecureStringToCoTaskMemAnsi Method
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Marshal.SecureStringToCoTaskMemAnsi Method (SecureString)

 

Copies the contents of a managed SecureString object to a block of memory allocated from the unmanaged COM task allocator.

Namespace:   System.Runtime.InteropServices
Assembly:  mscorlib (in mscorlib.dll)

[SecurityCriticalAttribute]
public static IntPtr SecureStringToCoTaskMemAnsi(
	SecureString s
)

Parameters

s
Type: System.Security.SecureString

The managed object to copy.

Return Value

Type: System.IntPtr

The address, in unmanaged memory, where the s parameter was copied to, or 0 if a null object was supplied.

Exception Condition
ArgumentNullException

The s parameter is null.

NotSupportedException

The current computer is not running Windows 2000 Service Pack 3 or later.

OutOfMemoryException

There is insufficient memory available.

The SecureStringToCoTaskMemAnsi method is useful for custom marshaling or when mixing managed and unmanaged code. Because this method allocates the unmanaged memory required for a string, always free the memory by calling ZeroFreeCoTaskMemAnsi. The characters of the string are copied as ANSI characters.

Notes to Callers:

This method is supported only on computers running Windows 2000 Service Pack 3 or later.

The following example uses the SecureStringToCoTaskMemAnsi method to marshal and decrypt the contents of a SecureString object to a block of unmanaged memory. It then uses the ZeroFreeCoTaskMemAnsi method to zero out and dispose the unmanaged block.

using System;
using System.Runtime.InteropServices;
using System.Security;

class MarshalExample
{
     static void Main()
     {
         IntPtr unmanagedRef = IntPtr.Zero;

          // Ask the user for a password.
          Console.Write("Please enter your password: ");

          SecureString passWord = GetPassword();

          Console.WriteLine("Copying and decrypting the string to unmanaged memory...");

          // Copy the Secure string to unmanaged memory (and decrypt it).
          unmanagedRef = Marshal.SecureStringToCoTaskMemAnsi(passWord);

          if (unmanagedRef != IntPtr.Zero)
          {
              Console.WriteLine("Zeroing out unmanaged memory...");

              Marshal.ZeroFreeCoTaskMemAnsi(unmanagedRef);
          }
          passWord.Dispose();

         Console.WriteLine("Done.");
     }

     public static SecureString GetPassword()
     {
         SecureString password = new SecureString();

         // get the first character of the password
         ConsoleKeyInfo nextKey = Console.ReadKey(true);

         while (nextKey.Key != ConsoleKey.Enter)
         {
             if (nextKey.Key == ConsoleKey.Backspace)
             {
                 if (password.Length > 0)
                 {
                     password.RemoveAt(password.Length - 1);

                     // erase the last * as well
                     Console.Write(nextKey.KeyChar);
                     Console.Write(" ");
                     Console.Write(nextKey.KeyChar);
                 }
             }
             else
             {
                 password.AppendChar(nextKey.KeyChar);
                 Console.Write("*");
             }

             nextKey = Console.ReadKey(true);
         }

         Console.WriteLine();

         // lock the password down
         password.MakeReadOnly();
         return password;
     }
}

SecurityCriticalAttribute

requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

.NET Framework
Available since 2.0
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