Marshal.SecureStringToCoTaskMemAnsi(SecureString) Method

Definition

Important

This API is not CLS-compliant.

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

C#
public static IntPtr SecureStringToCoTaskMemAnsi(System.Security.SecureString s);
C#
[System.CLSCompliant(false)]
public static IntPtr SecureStringToCoTaskMemAnsi(System.Security.SecureString s);
C#
[System.Security.SecurityCritical]
public static IntPtr SecureStringToCoTaskMemAnsi(System.Security.SecureString s);

Parameters

s
SecureString

The managed object to copy.

Returns

IntPtr

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

Attributes

Exceptions

The s parameter is null.

There is insufficient memory available.

Examples

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.

C#
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;
     }
}

Remarks

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.

Applies to

Product Versions
.NET Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 2.0, 2.1