[C#]파일 Random Access 빠르게 읽기 (readbyte,read)

        [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        private static extern bool DeviceIoControl(
            SafeFileHandle hDevice,
            int dwIoControlCode,
            IntPtr InBuffer,
            int nInBufferSize,
            IntPtr OutBuffer,
            int nOutBufferSize,
            ref int pBytesReturned,
            [In] ref NativeOverlapped lpOverlapped
        );

        static void MarkAsSparseFile(SafeFileHandle fileHandle)
        {
            int bytesReturned = 0;
            NativeOverlapped lpOverlapped = new NativeOverlapped();
            bool result =
                DeviceIoControl(
                    fileHandle,
                    590020, //FSCTL_SET_SPARSE,
                    IntPtr.Zero,
                    0,
                    IntPtr.Zero,
                    0,
                    ref bytesReturned,
                    ref lpOverlapped);
            if (result == false)
                throw new Win32Exception();
        }

MarkAsSparseFile(SafeFileHandle fileHandle)을 FileStream의 헨들러로 잡아주면됩니다.