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Marshal.SecureStringToCoTaskMemUnicode Method

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.


The s parameter is Nothing.


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
Imports System.Diagnostics
Imports System.Runtime.InteropServices
Imports System.Security
Imports System.Security.Principal
Imports System.Text

Module MarshalExample

    Sub Main(ByVal args() As String)

        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)

        Catch e As Exception

            If unmanagedRef <> IntPtr.Size Then

                Console.WriteLine("Zeroing out unmanaged memory...")


            End If

        End Try



    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

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

  • SecurityCriticalAttribute 

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

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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