unable to write at the specified file pointer

hey guys i m trying to write at a specified sector on a fat32 drive..
i m able to read from any sector by setfilepointer but wheen i write after moviing the pointer it still writes on the starting of the drive at 0 sector how can i write at any sectorr can any on help me plzzzzzz its very important very very ....

im totally stuck

Code:

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using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.IO;
using Microsoft.Win32.SafeHandles;
namespace FileLock
{
    struct fat32
    {


    }


    class fl
    {
        public int root = 0;
        public const uint FILE_SHARE_READ = 0x00000001;
        public const uint FILE_SHARE_WRITE = 0x00000002;
        public const uint FILE_SHARE_DELETE = 0x00000004;
        public const uint FILE_FLAG_WRITE_THROUGH = 0x80000000;
        public const uint FILE_FLAG_OVERLAPPED = 0x40000000;
        public const uint FILE_FLAG_NO_BUFFERING = 0x20000000;
        public const uint FILE_FLAG_RANDOM_ACCESS = 0x10000000;
        public const uint FILE_FLAG_SEQUENTIAL_SCAN = 0x08000000;
        public const uint FILE_ATTRIBUTE_NORMAL = 0x80;
        public const short INVALID_HANDLE_VALUE = -1;
        public const uint GENERIC_READ = 0x80000000;
        public const uint GENERIC_WRITE = 0x40000000;
        public const uint CREATE_NEW = 1;
        public const uint CREATE_ALWAYS = 2;
        public const uint OPEN_EXISTING = 3;


        public enum EMoveMethod : uint
        {
            Begin = 0,
            Current = 1,
            End = 2
        }
        //  [DllImport("coredll")]
        //static extern Boolean WriteFile(IntPtr fFile, Byte[] lpBuffer, UInt32 nNumberOfBytesToWrite,
        //      out UInt32 lpNumberOfBytesWritten, IntPtr lpOverlapped);
        [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        static extern unsafe uint SetFilePointer(
            [In] SafeFileHandle hFile,
            [In] int lDistanceToMove,
            [Out] int* lpDistanceToMoveHigh,
            [In] EMoveMethod dwMoveMethod);
        [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        static extern unsafe uint SetFilePointerB(
            [In] IntPtr File,
            [In] int lDistanceToMove,
            [Out] int* lpDistanceToMoveHigh,
            [In] EMoveMethod dwMoveMethod);

        [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        static extern uint SetFilePointer(
            [In] SafeFileHandle hFile,
            [In] int lDistanceToMove,
            [Out] out int lpDistanceToMoveHigh,
            [In] EMoveMethod dwMoveMethod);
 
        [DllImport("kernel32.dll")]///////////////Read File/////////////
        static extern bool ReadFile(SafeFileHandle hFile, byte[] lpBuffer,
          uint nNumberOfBytesToRead, out uint lpNumberOfBytesRead, IntPtr lpOverlapped);
             
        [DllImport("kernel32.dll")]//////writeFile function/////////////
        static extern bool WriteFile(SafeFileHandle hFile, byte[] lpBuffer,
          uint nNumberOfBytesToWrite, out uint lpNumberOfBytesWritten,
          [In] ref System.Threading.NativeOverlapped lpOverlapped);
     
       
      [DllImport("kernel32.dll", SetLastError = true)]///////CreateFile////////////
        static extern IntPtr CreateFileA(string lpFileName, uint dwDesiredAccess,
            uint dwShareMode, IntPtr lpSecurityAttributes, uint dwCreationDisposition,
            uint dwFlagsAndAttributes, IntPtr hTemplateFile);

        [DllImport("kernel32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall, SetLastError = true)]
        public static extern SafeFileHandle CreateFile(
              string lpFileName,
              uint dwDesiredAccess,
              uint dwShareMode,
              IntPtr SecurityAttributes,
              uint dwCreationDisposition,
              uint dwFlagsAndAttributes,
              IntPtr hTemplateFile
              );

        public SafeFileHandle ptr;
        public SafeFileHandle Connect(String a)
      {
        return  CreateFile(a, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, IntPtr.Zero, OPEN_EXISTING, FILE_FLAG_WRITE_THROUGH, IntPtr.Zero);
     
      }
        public string ReadString(Byte[] buff)
        {
          String temp="";
            for (int i = 0; i < buff.Length; i++)
            {
              if (i % 15 == 0)
              temp += "\n";
           
                  temp += String.Format("{0:X}", (int)buff[i]) + " ";
          //temp += buff[i]+"__";
            }
       
            return temp;
        }
        public Byte[] read(SafeFileHandle ptr)
        {
          Byte[] Buff = new System.Byte[512];
            FileStream lpt = new FileStream(ptr, FileAccess.ReadWrite);
            lpt.Read(Buff, 0, Buff.Length);
            return Buff;
        }

      public int RootStart(Byte[] buff)
        {
          string temp ="";
            temp += String.Format("{0:X}", (int)buff[15]) + String.Format("{0:X}", (int)buff[14]);
          int reserved = Convert.ToInt32(temp,16);
          int nof = buff[16];
          int secpF=0;
          if (buff[22] == 0)
          {
              temp = "";
              temp += String.Format("{0:X}", (int)buff[39]) + String.Format("{0:X}", (int)buff[38]) + String.Format("{0:X}", (int)buff[37]) + String.Format("{0:X}", (int)buff[36]);
              secpF = Convert.ToInt32(temp, 16);
          }
          else
          {
              secpF=Convert.ToInt32(((int)buff[22])+"",16);

          }
            return secpF*nof+reserved;
        }

        public unsafe void toRoot(SafeFileHandle ptr, int sector)
        {
        SetFilePointer(ptr,(sector*512),null,0 );
        }
     
        public unsafe string fileCheck(String fname,out int sector)
        {

            //toRoot(ptr, RootStart(read(ptr)));
            int sec=-1;
            string temp="";
            string temp2="";
            //temp = filename(read(ptr), "",i, out sec);
            Byte[] b = new byte[512];
                b=read(ptr);
            //  temp = filename(b, "", 0, out sec);
                //temp2 += temp + "  " + fname + string.Compare(temp, fname, true);

          for (int i =0; i<15; i++)
            {temp = filename(b, "",0, out sec);

                if (string.Compare(temp, fname, true) == 0)
                { sector = sec; temp2 = "found";
                b[sec] = 40;
                    uint x;
                    System.Threading.NativeOverlapped g=new System.Threading.NativeOverlapped();
                    SetFilePointer(ptr, 512*root, null, 0);
                    ReadFile(ptr,b, 512, out x, IntPtr.Zero);
               
                      b[11] = 40;
                  WriteFile(ptr, b, 512, out x, ref g);
                    break;
                }
                else
                    temp2+=temp+ "_____";
               
          //  temp2 += temp + "___";
            }
           
            sector = sec;
            return temp2;
        }



        public void reset()
        {
            ptr = Connect("\\\\.\\N:");

        }


        public string filename(byte[] buff, string s,int no,out int sec)
        {
            if (buff[0 + 32 * no] != 229 && buff[0 + 32 * no] != 00 && buff[0 + 32 * no] != 05)
            {

                if (buff[11 + 32 * no] != 15)
                {
                    String temp = "";
                    int i = 32 * no; int c = 0;
                    while (buff[i] != 32 && c < 8)
                    {
                        c++;
                        temp += (char)buff[i++] + "";
                    }
                    temp += ".";
                    temp += (char)buff[8 + 32 * no]; temp += (char)buff[9 + 32 * no]; temp += (char)buff[10 + 32 * no];
                    sec = (11 + 32 * no);
                    return temp;

                }
                else
                {
                    string temp = "";
                    int c = buff[0 + 32 * no] - 64;
                    if (c > 0)
                    {
                        int[] rec = new int[] { 1, 3, 5, 7, 9, 14, 16, 18, 20, 22, 24, 28, 30 };
                        for (int i = c; i > 0; i--)
                        {
                            foreach (int j in rec)
                            {
                                if (buff[j + 32 * (i - 1) + 32 * no] != 255)
                                    temp += (char)buff[j + 32 * (i - 1) + 32 * no];
                            }
                        }
                    }
                    else
                        temp = "LNF";

                    sec = (11+32 * (c + 1) + 32 * no);
                    return temp;
                }



            }
            else
            {
                sec = 0;
                return "error";

            }
               
               
               
             

        }








        public fl()
        {


            ptr = Connect("\\\\.\\N:");
            root = RootStart(read(ptr));
        }






    }
}
class con
{



}

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