urgent ----exception problem anyone solution

[vikrant3mahajan]

hey any one tell me the solution to the exception generated ..............in lpt.write line ...

using System.IO;
using Microsoft.Win32.SafeHandles;

using System;
using System.Threading;
using System;
using System.Runtime.InteropServices;
public class PrintFactory
{
    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;

    [DllImport("kernel32.dll", SetLastError = true)]
    static extern IntPtr CreateFile(string lpFileName, uint dwDesiredAccess,
        uint dwShareMode, IntPtr lpSecurityAttributes, uint dwCreationDisposition,
        uint dwFlagsAndAttributes, IntPtr hTemplateFile);
    
    [DllImport("msvcrt")]
    static extern int _getch();
    
    [DllImport("kernel32.dll", SetLastError = true)]
    static extern unsafe int WriteFile(IntPtr handle, IntPtr buffer,
      int numBytesToWrite, IntPtr numBytesWritten, NativeOverlapped* lpOverlapped);
    
    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 uint SetFilePointer(
        [In] SafeFileHandle hFile,
        [In] int lDistanceToMove,
        [Out] out int lpDistanceToMoveHigh,
        [In] EMoveMethod dwMoveMethod);
    [DllImport("kernel32.dll", BestFitMapping = true, CharSet = CharSet.Ansi)]
    static extern bool WriteFile(IntPtr hFile, System.Text.StringBuilder lpBuffer,
     uint nNumberOfBytesToWrite, out uint lpNumberOfBytesWritten,
     [In] ref System.Threading.NativeOverlapped lpOverlapped);

    [DllImport("kernel32.dll")]
    static extern bool WriteFile(IntPtr hFile, byte[] lpBuffer,
       uint nNumberOfBytesToWrite, out uint lpNumberOfBytesWritten,
       [In] ref System.Threading.NativeOverlapped lpOverlapped);



   
    public PrintFactory()
    {
        IntPtr ptr = CreateFile("\\\\.\\N:", GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, IntPtr.Zero, OPEN_EXISTING, FILE_FLAG_WRITE_THROUGH, IntPtr.Zero);
        //IntPtr ptr = CreateFile("\\\\.\\N:", GENERIC_READ | GENERIC_WRITE, 0, IntPtr.Zero, OPEN_EXISTING, 0, IntPtr.Zero);

        
        
        
        
        
        
        /* Is bad handle? INVALID_HANDLE_VALUE */
        if (ptr.ToInt32() == -1)
        {
            /* ask the framework to marshall the win32 error code to an exception */
            Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());
        }
        else
        {
            String Temp = "This is a test print";
         Byte[] Buff = new System.Byte[512];
            //Check to see if your printer support ASCII encoding or Unicode.
            FileStream lpt = new FileStream(ptr, FileAccess.ReadWrite); 
            //If unicode is supported, use the following:
          //  Buff = System.Text.Encoding.Unicode.GetBytes(Temp);
           // Buff = System.Text.Encoding.ASCII.GetBytes(Temp);
            uint outt; IntPtr p=(IntPtr)0;
            //System.Threading.NativeOverlapped b=0;
            //WriteFile(ptr,Buff,512,out outt,ref b);
            
    //        Buff = System.Text.Encoding.ASCII.GetBytes(prnCmdCut);
           /*

            lpt.Read(Buff, 0, Buff.Length);
            for (int i = 0; i < 512; i++)
            {
                try
                {
                    if (i &#37; 16 == 0)
                        Console.WriteLine();
                    Console.Write(String.Format("{0:X}", (int)Buff[i])+" ");
                   
                }
                catch (Exception e) { }
            }*/
            lpt.WriteByte(71);    --------------->this line generates exception
            lpt.Close();
           // Console.Write(Temp);
            _getch();
        }
    }
}
class enter
{



     public static void Main()
    {
        new PrintFactory();
  
        
    }
}

exception

IO operation will not work. Most likely the file will become too long or the handle was not opened to support synchronous IO operations.