I am trying to open a file from VB.NET with ZwCreateFile, but I get
STATUS_DATATYPE_MISALIGNMENT returned. It's hard to know which bits to post,
so apologies for the dump below:

<header stuff>
   <StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Auto, Pack:=1)> _
   Structure OBJECT_ATTRIBUTES
       Dim Length As Int32
       Dim RootDirectory As IntPtr
       Dim ObjectName As IntPtr
       Dim Attrs As ATTRIBUTES
       Dim SecurityDescriptor As IntPtr
       Dim SecurityQualityOfService As IntPtr
   End Structure

   <StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Auto, Pack:=1)> _
   Structure IO_STATUS_BLOCK
       Dim Status As NTSTATUS
       Dim Information As INFO
   End Structure

   <DllImport("ntdll", SetLastError:=True)> _
   Friend Function ZwCreateFile(ByRef FileHandle As IntPtr, _
                                ByVal DesiredAccess As ACCESS_MASK, _
                                ByVal ObjectAttributes As IntPtr, _
                                ByRef IoStatusBlock As IntPtr, _
                                ByVal AllocationSize As IntPtr, _
                                ByVal FileAttributes As FILE_ATTRIBUTE, _
                                ByVal ShareAccess As SHARE_ACCESS, _
                                ByVal CreateDisposition As
CREATE_DISPOSITION, _
                                ByVal CreateOptions As CREATE_OPTIONS, _
                                ByVal EaBuffer As IntPtr, _
                                ByVal EaLength As Integer) As NTSTATUS

   End Function

   Public Sub InitializeObjectAttributes(ByRef InitializedAttributes As
OBJECT_ATTRIBUTES, _
                                         ByVal ObjectName As String, _
                                         ByVal Attrs As ATTRIBUTES, _
                                         ByVal RootDirectory As IntPtr, _
                                         ByVal SecurityDescriptor As
IntPtr)

       InitializedAttributes.Length = Marshal.SizeOf(InitializedAttributes)
       InitializedAttributes.RootDirectory = RootDirectory
       InitializedAttributes.Attrs = Attrs
       InitializedAttributes.ObjectName =
Marshal.StringToHGlobalUni(ObjectName)
       InitializedAttributes.SecurityDescriptor = SecurityDescriptor
       InitializedAttributes.SecurityQualityOfService = New IntPtr(0)

   End Sub
</header stuff>

<code extract>
       Dim oa As OBJECT_ATTRIBUTES
       Dim objName As String

       Dim allocation As ATTRIBUTES

       objName = "test.txt"
       allocation = ATTRIBUTES.OBJ_CASE_INSENSITIVE Or
API.ATTRIBUTES.OBJ_OPENIF

       InitializeObjectAttributes(oa, objName, allocation, New IntPtr(0),
New IntPtr(0))

       Dim da As ACCESS_MASK
       Dim poa As IntPtr

       Dim ns As NTSTATUS

       Dim fileHandle As IntPtr
       Dim piosb As IntPtr
       Dim palloc As IntPtr
       Dim fa As FILE_ATTRIBUTE
       Dim sa As SHARE_ACCESS
       Dim cd As CREATE_DISPOSITION
       Dim co As CREATE_OPTIONS
       Dim eb As IntPtr
       Dim el As Integer
       Dim iosb As IO_STATUS_BLOCK

       ' Set up da
       da = API.ACCESS_MASK.SYNCHRONIZE Or API.ACCESS_MASK.GENERIC_READ

       ' set up poa
       poa = Marshal.AllocHGlobal(Marshal.SizeOf(oa))
       Marshal.StructureToPtr(oa, poa, False)

       ' set up piosb
       piosb = Marshal.AllocHGlobal(Marshal.SizeOf(iosb))

       ' Set up palloc
       palloc = New IntPtr(0)

       fa = API.FILE_ATTRIBUTE.FILE_ATTRIBUTE_NORMAL
       sa = API.SHARE_ACCESS.FILE_SHARE_READ Or
API.SHARE_ACCESS.FILE_SHARE_WRITE
       cd = API.CREATE_DISPOSITION.FILE_OPEN
       co = API.CREATE_OPTIONS.FILE_NON_DIRECTORY_FILE Or
API.CREATE_OPTIONS.FILE_SYNCHRONOUS_IO_NONALERT

       eb = New IntPtr(0)
       el = 0

       ns = ZwCreateFile(fileHandle, da, poa, piosb, palloc, fa, sa, cd,
co, eb, el)
</code extract>

Has anybody got an idea why I get this return code? I am quite prepared to
believe that some of my definitions might not be quite right, but I have
tried all sorts of things, all to no avail.

An example of how it should be done - in any language - would be every bit
as helpful.

TIA

Charles