C# Signature:

[DllImport("advapi32.dll", SetLastError=true)]
static extern bool ConvertStringSidToSid(
            string StringSid,
            out IntPtr ptrSid
            );

VB Signature:

    Private Declare Auto Function ConvertSidToStringSid Lib "advapi32.dll" ( _
    ByVal Sid As IntPtr, _
    ByRef StringSid As IntPtr _
    ) As Boolean
    Private Declare Function GetLengthSid Lib "advapi32.dll" Alias "GetLengthSid" (ByVal pSID As IntPtr) As Integer

User-Defined Types:

None.

Notes:

    'BOOL ConvertSidToStringSid(
    '  PSID Sid,
    '  LPTSTR* StringSid
    ');

Tips & Tricks:

Please add some!

VB.Net Sample Code:

    Dim Sid, SidPtr As IntPtr
    Dim SidString As String

    ' convert the SID to a string
    If Environment.Version.Major = 4 Then
        SidString = ConvertSidToStringSidNT(Sid)
    Else
        If ConvertSidToStringSid(Sid, SidPtr) = False Then
        Exit Sub
        End If
        SidString = Marshal.PtrToStringAuto(SidPtr)
        Marshal.FreeHGlobal(SidPtr)
    End If

VB.Net Sample Code:

Private Function ConvertSidFromStringToByte(ByVal i_Sid As String, ByRef io_sid As Byte()) As Boolean

    '*********************************************************************
    '* Converts a sid string to a byte array
    '*********************************************************************

    Dim result As Boolean
    Dim m_IntPtr As IntPtr
    Dim res As Integer

    Try
        res = ConvertStringSidToSid(i_Sid, m_IntPtr)

        If res <> -1 Then
        Dim m_LastWin32Error As Integer = System.Runtime.InteropServices.Marshal.GetLastWin32Error()
        Dim m_LastWin32ErrorString As String = System.Runtime.InteropServices.Marshal.GetLastWin32Error.ToString
        Console.WriteLine("Error: " & m_LastWin32ErrorString)
        Else
        Dim m_SidLength As Integer = GetLengthSid(m_IntPtr) - 1     'Aint 100% sure about -1
        ReDim io_sid(m_SidLength)
        System.Runtime.InteropServices.Marshal.Copy(m_IntPtr, io_sid, 0, m_SidLength)
        result = True
        End If

    Catch ex As Exception

    Finally
        System.Runtime.InteropServices.Marshal.FreeHGlobal(m_IntPtr)
    End Try

    Return result

    End Function

Alternative Managed API:

    'typedef struct _SID_IDENTIFIER_AUTHORITY {
    '  BYTE Value[6];
    '} SID_IDENTIFIER_AUTHORITY, *PSID_IDENTIFIER_AUTHORITY;
    Structure SID_IDENTIFIER_AUTHORITY
    <MarshalAs(UnmanagedType.ByValArray, SizeConst:=6)> Dim Value() As Byte
    End Structure

    'BOOL IsValidSid(
    '  PSID pSid
    ');
    Private Declare Function IsValidSid Lib "advapi32.dll" ( _
    ByVal pSid As IntPtr _
    ) As Boolean

    'PSID_IDENTIFIER_AUTHORITY GetSidIdentifierAuthority(
    '  PSID pSid
    ');
    Private Declare Function GetSidIdentifierAuthority Lib "advapi32.dll" ( _
    ByVal pSid As IntPtr _
    ) As IntPtr

    'PUCHAR GetSidSubAuthorityCount(
    '  PSID pSid
    ');
    Private Declare Function GetSidSubAuthorityCount Lib "advapi32.dll" ( _
    ByVal pSid As IntPtr _
    ) As IntPtr

    'PDWORD GetSidSubAuthority(
    '  PSID pSid,
    '  DWORD nSubAuthority
    ');
    Private Declare Function GetSidSubAuthority Lib "advapi32.dll" ( _
    ByVal pSid As IntPtr, _
    ByVal nSubAuthority As Integer _
    ) As IntPtr

    ' a WinNT version of the ConvertSidToStringSid function
    Function ConvertSidToStringSidNT(ByVal Sid As IntPtr) As String
    Dim ans As String
    Dim psia As SID_IDENTIFIER_AUTHORITY
    Dim i, num, temp As Integer
    Dim top As Long
    Dim iptr As IntPtr

    If Not IsValidSid(Sid) Then
        Return ans
    End If

    ans = "S-1-"

    ' Get the top level authority
    iptr = GetSidIdentifierAuthority(Sid)
    psia = Marshal.PtrToStructure(iptr, GetType(SID_IDENTIFIER_AUTHORITY))

    ' How many sub authorities?
    iptr = GetSidSubAuthorityCount(Sid)
    num = Marshal.ReadInt16(iptr)

    ' hex version of the top authority?
    If psia.Value(0) <> 0 And psia.Value(1) <> 0 Then
        ans &= Hex(psia.Value(0))
        ans &= Hex(psia.Value(1)).PadLeft(2, "0")
        ans &= Hex(psia.Value(2)).PadLeft(2, "0")
        ans &= Hex(psia.Value(3)).PadLeft(2, "0")
        ans &= Hex(psia.Value(4)).PadLeft(2, "0")
        ans &= Hex(psia.Value(5)).PadLeft(2, "0")
    Else
        top = psia.Value(5)
        top += psia.Value(4) * 256
        top += psia.Value(3) * 256 * 256
        top += psia.Value(2) * 256 * 256 * 256
        ans &= top.ToString
    End If

    For i = 0 To num - 1
        iptr = GetSidSubAuthority(Sid, i)
        temp = Marshal.ReadInt32(iptr)
        ans &= "-" & temp.ToString
    Next

    Return ans
    End Function