Geek asks and answers

Is there a .NET API to return the equivalent extended path string for a given path?

In NTFS, I can prefix the path with a character sequence \\?\to indicate that it is a path that exceeds the limit of 260 characters; as such, the file system will correctly interpret the path and not elevate PathTooLongException.

(see http://msdn.microsoft.com/en-us/library/aa365247%28VS.85%29.aspx#maxpath for more information)

Is there a .NET API that will prefix my path lines with this sequence, or am I stuck writing my own?

In essence, I am looking for a method equivalent to the following.

static string ToExtendedPath(string path)
{
    if(Path.IsPathRooted(path))
    {
        return @"\\?\" + path;
    }

    return Path.Combine(@"\\?\", path);
}
+4
source share
2 answers

, .NET API, "" . (, , ).

: , .NET () . , API . API . , . MSDN.

, , - API (, CreateFile) .NET.

+6

, @helge-klein , .Net API 260 , , 260 max_path.

[] DotNet 4.6.2: System.IO.LongPath,

Windows 10 Creators Update ​​( ), MoveFileEx W, , dotnetReferenceSource DotNet Framework System.IO.File:

#if FEATURE_CORESYSTEM
    [DllImport(KERNEL32, SetLastError=true, CharSet=CharSet.Auto, BestFitMapping=false)]
    [ResourceExposure(ResourceScope.Machine)]
    private static extern bool MoveFileEx(String src, String dst, uint flags);

    internal static bool MoveFile(String src, String dst)
    {
        return MoveFileEx(src, dst, 2 /* MOVEFILE_COPY_ALLOWED */);
    }
#else // FEATURE_CORESYSTEM
    [DllImport(KERNEL32, SetLastError=true, CharSet=CharSet.Auto, BestFitMapping=false)]
    [ResourceExposure(ResourceScope.Machine)]
    internal static extern bool MoveFile(String src, String dst);
#endif // FEATURE_CORESYSTEM

LinqPad MoveFile ( pinvoke)

void Main()
{
    //Create 3 files: in c:\temp\test\
    //testsrc0.txt, testsrc1.txt and testsrc2.txt
    //"\\?\UNC\server\share", 
    string src0File = @"\\?\UNC\127.0.0.1\c$\temp\test\testsrc0.txt";
    string dst0File = @"\\?\UNC\127.0.0.1\c$\temp\test\testdst0.txt";
    string dst0FileDotNet = @"c:\temp\test\testdst0.txt";
    string src1File = @"\\?\c:\temp\test\testsrc1.txt";
    string dst1File = @"\\?\c:\temp\test\testdst1.txt";
    string dst1FileDotNet = @"c:\temp\test\testdst1.txt";
    string src2File = @"\\?\\127.0.0.1\c$\temp\test\testsrc2.txt";
    string dst2File = @"\\?\\127.0.0.1\c$\temp\test\testdst2.txt";
    string dst2FileDotNet = @"c:\temp\test\testdst2.txt";

    MoveFileEx(src0File, dst0File, MoveFileFlags.MOVEFILE_REPLACE_EXISTING);
    System.IO.File.Exists(dst0File).Dump("File0 Exists");//FALSE
    System.IO.File.Exists(dst0FileDotNet).Dump("File0 Exists");//TRUE    

    MoveFileEx(src1File, dst1File, MoveFileFlags.MOVEFILE_REPLACE_EXISTING);
    System.IO.File.Exists(dst1File).Dump("File1 Exists");//FALSE
    System.IO.File.Exists(dst1FileDotNet).Dump("File1 Exists");//TRUE    

    MoveFileEx(src2File, dst2File, MoveFileFlags.MOVEFILE_REPLACE_EXISTING);
    System.IO.File.Exists(dst2File).Dump("File2 Exists");//FALSE
    System.IO.File.Exists(dst2FileDotNet).Dump("File2 Exists");//FALSE - as missing UNC keyword
    System.Runtime.InteropServices.Marshal.GetLastWin32Error().Dump("ERROR:");//3 == ERROR_PATH_NOT_FOUND
}

[Flags]
enum MoveFileFlags
{
    MOVEFILE_REPLACE_EXISTING = 0x00000001,
    MOVEFILE_COPY_ALLOWED = 0x00000002,
    MOVEFILE_DELAY_UNTIL_REBOOT = 0x00000004,
    MOVEFILE_WRITE_THROUGH = 0x00000008,
    MOVEFILE_CREATE_HARDLINK = 0x00000010,
    MOVEFILE_FAIL_IF_NOT_TRACKABLE = 0x00000020
}

// Define other methods and classes here
[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
static extern bool MoveFileEx(string lpExistingFileName, string lpNewFileName, MoveFileFlags dwFlags);

UNC- UNC. \?\UNC\

0

More articles:


All Articles