Marshal.SecureStringToCoTaskMemUnicode 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)

Public Shared Function SecureStringToCoTaskMemUnicode (
	s As SecureString
) As IntPtr


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

The s parameter is null.


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


There is insufficient memory available.

The SecureStringToCoTaskMemUnicode 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 the ZeroFreeCoTaskMemUnicode method. The characters of the string are copied as Unicode characters.

Notes to Callers:

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

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

Imports System.Runtime.InteropServices
Imports System.Security

Module Example
    Public Sub Main()
        Dim unmanagedRef As IntPtr
        ' Ask the user for a password.
        Console.Write("Please enter your password: ")
        Dim passWord As SecureString = GetPassword()

        Console.WriteLine("Copying and decrypting the string to unmanaged memory...")
        ' Copy the Secure string to unmanaged memory (and decrypt it).
        unmanagedRef = Marshal.SecureStringToCoTaskMemUnicode(passWord)

        If unmanagedRef <> IntPtr.Size Then
            Console.WriteLine("Zeroing out unmanaged memory...")
        End If
    End Sub

    Function GetPassword() As SecureString
        Dim password As New SecureString()

        ' Get the first character of the password.
        Dim nextKey As ConsoleKeyInfo = Console.ReadKey(True)
        While nextKey.Key <> ConsoleKey.Enter
            If nextKey.Key = ConsoleKey.BackSpace Then
                If password.Length > 0 Then
                    password.RemoveAt(password.Length - 1)

                    ' Erase the last * as well.
                    Console.Write(" ")
                End If
            End If

            nextKey = Console.ReadKey(True)
        End While

        ' lock the password down
        Return password
    End Function
End Module
' The example displays output like the following:
'       Please enter your password: **********
'       Copying and decrypting the string to unmanaged memory...
'       Zeroing out unmanaged memory...
'       Done.


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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