DeviceIOControl funtion have exception when that return mft
<p>I write this class for access volumedata.  </p>

<pre><code>class GetFiles
    {
        public void  getlist()
            {
            NTFS_VOLUME_DATA_BUFFER volumData=new NTFS_VOLUME_DATA_BUFFER();

            uint Resultsize=0;
                IntPtr hroot = GetFiles.CreateFile(@"\\.\C:\", 0,
                    pinvok.FILE_SHARE_READ | pinvok.FILE_SHARE_WRITE,
                    IntPtr.Zero,
                    pinvok.OPEN_EXISTING,
                    pinvok.FILE_FLAG_BACKUP_SEMANTICS,
                    IntPtr.Zero);

                GetFiles.DeviceIoControl(hroot,
                    pinvok.FSCTL_GET_NTFS_VOLUME_DATA,
                    IntPtr.Zero,0,
                   out volumData,(uint)Marshal.SizeOf(volumData),
                    out Resultsize,IntPtr.Zero
                    );              
         }

        public struct pinvok
        {          
            public const UInt32 FILE_SHARE_READ = 0x00000001;
            public const UInt32 FILE_SHARE_WRITE = 0x00000002;
            public const UInt32 FILE_ATTRIBUTE_DIRECTORY = 0x00000010;
            public const UInt32 OPEN_EXISTING = 3;
            public const UInt32 FILE_FLAG_BACKUP_SEMANTICS = 0x02000000;
            public const Int32 INVALID_HANDLE_VALUE = -1;
            public const UInt32 FSCTL_QUERY_USN_JOURNAL = 0x000900f4;
            public const UInt32 FSCTL_ENUM_USN_DATA = 0x000900b3;
            public const UInt32 FSCTL_CREATE_USN_JOURNAL = 0x000900e7;
            public const UInt32 FSCTL_GET_NTFS_VOLUME_DATA = 0x00090064;
        }
     [StructLayout(LayoutKind.Auto,CharSet=CharSet.Unicode)]
        public struct NTFS_VOLUME_DATA_BUFFER
        {
            public long VolumeSerialNumber;
            public long NumberSectors;
            public long TotalClusters;
            public long FreeClusters;
            public long TotalReserved;
            public uint BytesPerSector;
            public uint BytesPerCluster;
            public uint BytesPerFileRecordSegment;
            public uint ClustersPerFileRecordSegment;
            public long MftValidDataLength;
            public long MftStartLcn;
            public long Mft2StartLcn;
            public long MftZoneStart;
            public long MftZoneEnd;

        }


        [DllImport("kernel32.dll", SetLastError = true)]
            public static extern IntPtr CreateFile(string lpFileName, uint dwDesiredAccess,
                                                      uint dwShareMode, IntPtr lpSecurityAttributes,
                                                      uint dwCreationDisposition, uint dwFlagsAndAttributes,
                                                      IntPtr hTemplateFile);

        [DllImport("kernel32.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)]
        [return: MarshalAs(UnmanagedType.Bool)]     
        public static extern bool DeviceIoControl(IntPtr hDevice,
                uint dwIoControlCode, IntPtr lpInBuffer, uint nInBufferSize,
                out NTFS_VOLUME_DATA_BUFFER lpOutBuffer, uint nOutBufferSize,
                out uint lpBytesReturned, IntPtr lpOverlapped);

    }
</code></pre>

<p>I encountered exeception:</p>

<p><code>Type 'AccessMFT.GetFiles+NTFS_VOLUME_DATA_BUFFER' cannot be marshaled as an unmanaged structure; no meaningful size or offset can be computed.</code></p>
