C# Signature:

[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);

User-Defined Types:

None.

Notes:

You need to add "using System.IO;" in the class from wich you are importing the CreateFile function.

Tips & Tricks:

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

For example:

IntPtr ptr = CreateFile(filename, FileAccess.ReadWrite, FileShare.ReadWrite, IntPtr.Zero, FileMode.Open, 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.GetLastWin32Error());
}
else
{
    return new FileStream(ptr,access);
}

Another useful thing you can do with the IntrPtr is use it to open a FileStream in an asynchronous manner (Note there is an alternative consturctor for asynchronous FileStream's, but it doesn't seem to work!)

You'll want to call CloseHandle on what you opened if you don't turn it into a FileStream.

Alternative Managed API:

System.IO.File and System.IO.FileInfo