WINAPI FindFirstFile & FindNextFile problem

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• 

  Vulpes15y agoPosted Mar 25, 2011, 9:25 AM

  Accepted answer

  I've just been playing around with this some more and found that if you add the following attribute to the struct in your original program then it works fine!
  
  [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
  
  I think this is because you're using the CharSet.Auto versions of the functions which default to ANSI. As there was no attribute, the strings would have been marshalled to unicode.
  
  
  
• J

  Jorge15y agoPosted Mar 25, 2011, 9:37 AM

  Thank you very much, Vulpes! Your first reply worked with one minor adjustment, I only had to trim the trailing nulls from the string in the line: sw.WriteLine(Encoding.Unicode.GetString(wfd.cFileName)); The second reply was spot on! Thanks again
• 

  Vulpes15y agoPosted Mar 25, 2011, 9:05 AM

  I think the problem there is that the API functions are unable to write properly to the strings within the struct bearing in mind that strings are immutable in .NET. StringBuilder doesn't work either but I did manage to get it to work using byte arrays (changes are commented):
  
  using System;
  using System.IO;
  using System.Runtime.InteropServices;
  using System.Text; // added this
  
  
  namespace DirectoryWINAPI
  {
     [StructLayout(LayoutKind.Sequential)] // added this
     struct WIN32_FIND_DATA
     {
         public uint dwFileAttributes;
         public System.Runtime.InteropServices.ComTypes.FILETIME ftCreationTime;
         public System.Runtime.InteropServices.ComTypes.FILETIME ftLastAccessTime;
         public System.Runtime.InteropServices.ComTypes.FILETIME ftLastWriteTime;
         public uint nFileSizeHigh;
         public uint nFileSizeLow;
         public uint dwReserved0;
         public uint dwReserved1;
         [MarshalAs(UnmanagedType.ByValArray, SizeConst = 260)] // change here
         public byte[] cFileName;                               // ditto
         [MarshalAs(UnmanagedType.ByValArray, SizeConst = 14)]  // ditto
         public byte[] cAlternateFileName;                      // ditto
     }
  
  
     class Program
     {
         [DllImport("kernel32", CharSet = CharSet.Auto)]
         public static extern IntPtr FindFirstFile(string lpFileName, out WIN32_FIND_DATA lpFindFileData);
  
  
         [DllImport("kernel32", CharSet = CharSet.Auto)]
         public static extern bool FindNextFile(IntPtr hFindFile, out WIN32_FIND_DATA lpFindFileData);
  
  
         [DllImport("kernel32", CharSet = CharSet.Auto)]
         public static extern bool FindClose(IntPtr hFindFile);
  
  
         static void Main(string[] args)
         {
             StreamWriter sw = new StreamWriter("dir.txt", false);
             string dir = Path.GetFullPath(System.IO.Directory.GetCurrentDirectory());
             WIN32_FIND_DATA wfd = new WIN32_FIND_DATA();
             IntPtr h = FindFirstFile((dir + @"\*.*"), out wfd);
             while (FindNextFile(h, out wfd))
                 sw.WriteLine(Encoding.Unicode.GetString(wfd.cFileName)); // change here
             FindClose(h);
             sw.Flush();
             sw.Close();
         }
     }
  }