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CreateFile (kernel32)

C# Signature:

[DllImport("kernel32.dll", SetLastError=true, CharSet=CharSet.Auto)]
public static extern IntPtr CreateFile(
    string lpFileName,
    EFileAccess dwDesiredAccess,
    EFileShare dwShareMode,
    IntPtr lpSecurityAttributes,
    ECreationDisposition dwCreationDisposition,
    EFileAttributes dwFlagsAndAttributes,
    IntPtr hTemplateFile);

VB.Net Signature:

<DllImport("kernel32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> Private Shared Function CreateFile(ByVal lpFileName As String, ByVal dwDesiredAccess As EFileAccess, ByVal dwShareMode As EFileShare, ByVal lpSecurityAttributes As IntPtr, ByVal dwCreationDisposition As ECreationDisposition, ByVal dwFlagsAndAttributes As EFileAttributes, ByVal hTemplateFile As IntPtr) As IntPtr
End Function

User-Defined Types:

public enum EFileAccess : uint
    GenericRead    = 0x80000000,
    GenericWrite   = 0x40000000,
    GenericExecute = 0x20000000,
    GenericAll     = 0x10000000

public enum EFileShare : uint
    None   = 0x00000000,
    Read   = 0x00000001,
    Write  = 0x00000002,
    Delete = 0x00000004

public enum ECreationDisposition : uint
    New         = 1,
    CreateAlways    = 2,
    OpenExisting    = 3,
    OpenAlways      = 4,
    TruncateExisting= 5

public enum EFileAttributes : uint
    Readonly     = 0x00000001,
    Hidden       = 0x00000002,
    System       = 0x00000004,
    Directory    = 0x00000010,
    Archive      = 0x00000020,
    Device       = 0x00000040,
    Normal       = 0x00000080,
    Temporary    = 0x00000100,
    SparseFile       = 0x00000200,
    ReparsePoint     = 0x00000400,
    Compressed       = 0x00000800,
    Offline      = 0x00001000,
    NotContentIndexed= 0x00002000,
    Encrypted    = 0x00004000,
    Write_Through    = 0x80000000,
    Overlapped       = 0x40000000,
    NoBuffering      = 0x20000000,
    RandomAccess     = 0x10000000,
    SequentialScan   = 0x08000000,
    DeleteOnClose    = 0x04000000,
    BackupSemantics  = 0x02000000,
    PosixSemantics   = 0x01000000,
    OpenReparsePoint = 0x00200000,
    OpenNoRecall     = 0x00100000,
    FirstPipeInstance= 0x00080000

Instead of the enum "EFileAttributes" supplied on this page, you can also use "System.IO.FileAttributes". The enum values are identical up to "Encrypted".

This is NOT true for "EFileAccess" and "System.IO.FileAccess"!



Tips & Tricks:

You can use the IntPtr from Createfile with FileStream. This is usefull for opening devices such as Com1:, Lpt1: and Prn.

Unlike the FileStream ctor, CreateFile also allows you to open or create Windows 2000 sub-streams (e.g. "C:\Temp.dat:SubStream1").

For example:

IntPtr ptr = CreateFile(filename,access, share,0, mode,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 */
    return new FileStream(ptr,access);

Microsoft .NET Framework 2.0 Changes

If you are using version 2.0 of the .NET framework, you will need to make a few changes because of obsolete methods in the release for OpenFile. You can no longer try the good old

    return new FileStream(hDrv, FileAccess.Read);

unless the hDrv is of the new SafeFileHandle type.

Simply replace the IntPtr's with SafeFileHandle - the updated signature is:

    [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    static extern SafeFileHandle CreateFile(
        string fileName,
        [MarshalAs(UnmanagedType.U4)] FileAccess fileAccess,
        [MarshalAs(UnmanagedType.U4)] FileShare fileShare,
        IntPtr securityAttributes,
        [MarshalAs(UnmanagedType.U4)] FileMode creationDisposition,
        [MarshalAs(UnmanagedType.U4)] EFileAttributes flags,
        IntPtr template);

And also make sure that you import Microsoft.Win32.SafeHandles. The other code as below in the Alternative Managed API will work the same.

Alternative Managed API:

Do you know one? Please contribute it!

CreateFile on MSDN
FileStream on MSDN
Marshal on MSDN

You're doing this the hard way. Just define it like this:

    [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    static extern IntPtr CreateFile(
        string fileName,
        [MarshalAs(UnmanagedType.U4)] FileAccess fileAccess,
        [MarshalAs(UnmanagedType.U4)] FileShare fileShare,
        int securityAttributes,
        [MarshalAs(UnmanagedType.U4)] FileMode creationDisposition,
        int flags,
        IntPtr template);

Now you can use the normal .NET enums that people are familiar with

Thought I post a sample code to help out anyone else who may need help : )

/// Sample code provided as is.
/// Sample Composed by Wijaya "Wi" T
/// References:
///    Usage:  
///        Initialize this class in your main code (see below),
///        and walla you are now printing!
///        e.g.:
///        PrintFactory objPrintFactory = new PrintFactory();
///    Thank you:
///        Thank you all who have been contributing to printing to LPT port.
///        God Bless you! : )
///    Addt'l info:
///        Don't forget to reference:
///            using System.Runtime.InteropServices;
///            using System.IO;
public class PrintFactory
   public const short 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);

   public PrintFactory()
      IntPtr ptr = CreateFile("LPT1", 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 */
     String Temp = "This is a test print";
     //This is the cut command on Star TSP 600 Printer
     char[] prnCmdCut = {(char)27, (char)100, (char)51};                
     FileStream lpt = new FileStream(ptr,FileAccess.ReadWrite);
     Byte[] Buff = new Byte[1024];
     //Check to see if your printer support ASCII encoding or Unicode.
     //If unicode is supported, use the following:
     //Buff = System.Text.Encoding.Unicode.GetBytes(Temp);
     Buff = System.Text.Encoding.ASCII.GetBytes(Temp);
     Buff = System.Text.Encoding.ASCII.GetBytes(prnCmdCut);


Where is the secutityAttributes?! It's not to uncommon to want a file handle to be inheritable (e.g. you want to pass a handle to a server component like something running as a "servicedComponent" or a service...) and by using the securityAttributes this can be done...


Note that on win98, mapping the parameters to FileAccess and FileShare will cause CreateFileA to fail. I found this out the hard way, banging my head against a very slow win98 machine across an even slow connection. Instead use the EFileAccess, and EFileShare enumeration constants that match the windows constants ( as mentioned earlier in the article ).


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