C'è una parte nelle mie app che mostra il percorso del file caricato dall'utente tramite OpenFileDialog. Sta occupando troppo spazio per visualizzare l'intero percorso, ma non voglio visualizzare solo il nome del file in quanto potrebbe essere ambiguo. Quindi preferirei mostrare il percorso del file relativo alla directory assembly / exe.

Ad esempio, l'assembly risiede in C:\Program Files\Dummy Folder\MyPrograme il file in C:\Program Files\Dummy Folder\MyProgram\Data\datafile1.datquel momento vorrei che mostrasse .\Data\datafile1.dat. Se il file è in C:\Program Files\Dummy Folder\datafile1.dat, allora vorrei ..\datafile1.dat. Ma se il file si trova nella directory radice o 1 directory sotto radice, quindi visualizzare il percorso completo.

Quale soluzione consiglieresti? Regex?

Fondamentalmente voglio visualizzare informazioni utili sul percorso del file senza occupare troppo spazio sullo schermo.

EDIT: solo per chiarire un po 'di più. Lo scopo di questa soluzione è aiutare l'utente o me stesso a sapere quale file ho caricato per ultimo e all'incirca da quale directory era. Sto usando una casella di testo di sola lettura per visualizzare il percorso. Il più delle volte, il percorso del file è molto più lungo dello spazio di visualizzazione della casella di testo. Il percorso dovrebbe essere informativo ma non abbastanza importante da occupare più spazio sullo schermo.

Il commento di Alex Brault è stato buono, così come Jonathan Leffler. La funzione Win32 fornita da DavidK aiuta solo con parte del problema, non interamente, ma grazie comunque. Per quanto riguarda la soluzione di James Newton-King, ci proverò più tardi quando sarò libero.

.NET Core 2.0 Path.GetRelativePathlo usa altrimenti.

/// <summary>
/// Creates a relative path from one file or folder to another.
/// </summary>
/// <param name="fromPath">Contains the directory that defines the start of the relative path.</param>
/// <param name="toPath">Contains the path that defines the endpoint of the relative path.</param>
/// <returns>The relative path from the start directory to the end path or <c>toPath</c> if the paths are not related.</returns>
/// <exception cref="ArgumentNullException"></exception>
/// <exception cref="UriFormatException"></exception>
/// <exception cref="InvalidOperationException"></exception>
public static String MakeRelativePath(String fromPath, String toPath)
{
    if (String.IsNullOrEmpty(fromPath)) throw new ArgumentNullException("fromPath");
    if (String.IsNullOrEmpty(toPath))   throw new ArgumentNullException("toPath");

    Uri fromUri = new Uri(fromPath);
    Uri toUri = new Uri(toPath);

    if (fromUri.Scheme != toUri.Scheme) { return toPath; } // path can't be made relative.

    Uri relativeUri = fromUri.MakeRelativeUri(toUri);
    String relativePath = Uri.UnescapeDataString(relativeUri.ToString());

    if (toUri.Scheme.Equals("file", StringComparison.InvariantCultureIgnoreCase))
    {
        relativePath = relativePath.Replace(Path.AltDirectorySeparatorChar, Path.DirectorySeparatorChar);
    }

    return relativePath;
}

Un po 'tardi alla domanda, ma avevo solo bisogno di questa funzione. Concordo con DavidK sul fatto che, poiché esiste una funzione API integrata che lo fornisce, è necessario utilizzarlo. Ecco un wrapper gestito per questo:

public static string GetRelativePath(string fromPath, string toPath)
{
    int fromAttr = GetPathAttribute(fromPath);
    int toAttr = GetPathAttribute(toPath);

    StringBuilder path = new StringBuilder(260); // MAX_PATH
    if(PathRelativePathTo(
        path,
        fromPath,
        fromAttr,
        toPath,
        toAttr) == 0)
    {
        throw new ArgumentException("Paths must have a common prefix");
    }
    return path.ToString();
}

private static int GetPathAttribute(string path)
{
    DirectoryInfo di = new DirectoryInfo(path);
    if (di.Exists)
    {
        return FILE_ATTRIBUTE_DIRECTORY;
    }

    FileInfo fi = new FileInfo(path);
    if(fi.Exists)
    {
        return FILE_ATTRIBUTE_NORMAL;
    }

    throw new FileNotFoundException();
}

private const int FILE_ATTRIBUTE_DIRECTORY = 0x10;
private const int FILE_ATTRIBUTE_NORMAL = 0x80;

[DllImport("shlwapi.dll", SetLastError = true)]
private static extern int PathRelativePathTo(StringBuilder pszPath, 
    string pszFrom, int dwAttrFrom, string pszTo, int dwAttrTo);

Risposta di .NET Core 2.0

.NET Core 2.0 ha Path.GetRelativePath che può essere utilizzato in questo modo:

var relativePath = Path.GetRelativePath(
    @"C:\Program Files\Dummy Folder\MyProgram",
    @"C:\Program Files\Dummy Folder\MyProgram\Data\datafile1.dat");

Nell'esempio sopra, la relativePathvariabile è uguale a Data\datafile1.dat.

Risposta .NET alternativa

La soluzione di @ Dave non funziona quando i percorsi dei file non terminano con un carattere barra ( /) che può verificarsi se il percorso è un percorso di directory. La mia soluzione risolve questo problema e utilizza anche la Uri.UriSchemeFilecostante anziché la codifica effettiva "FILE".

/// <summary>
/// Creates a relative path from one file or folder to another.
/// </summary>
/// <param name="fromPath">Contains the directory that defines the start of the relative path.</param>
/// <param name="toPath">Contains the path that defines the endpoint of the relative path.</param>
/// <returns>The relative path from the start directory to the end path.</returns>
/// <exception cref="ArgumentNullException"><paramref name="fromPath"/> or <paramref name="toPath"/> is <c>null</c>.</exception>
/// <exception cref="UriFormatException"></exception>
/// <exception cref="InvalidOperationException"></exception>
public static string GetRelativePath(string fromPath, string toPath)
{
    if (string.IsNullOrEmpty(fromPath))
    {
        throw new ArgumentNullException("fromPath");
    }

    if (string.IsNullOrEmpty(toPath))
    {
        throw new ArgumentNullException("toPath");
    }

    Uri fromUri = new Uri(AppendDirectorySeparatorChar(fromPath));
    Uri toUri = new Uri(AppendDirectorySeparatorChar(toPath));

    if (fromUri.Scheme != toUri.Scheme)
    {
        return toPath;
    }

    Uri relativeUri = fromUri.MakeRelativeUri(toUri);
    string relativePath = Uri.UnescapeDataString(relativeUri.ToString());

    if (string.Equals(toUri.Scheme, Uri.UriSchemeFile, StringComparison.OrdinalIgnoreCase))
    {
        relativePath = relativePath.Replace(Path.AltDirectorySeparatorChar, Path.DirectorySeparatorChar);
    }

    return relativePath;
}

private static string AppendDirectorySeparatorChar(string path)
{
    // Append a slash only if the path is a directory and does not have a slash.
    if (!Path.HasExtension(path) &&
        !path.EndsWith(Path.DirectorySeparatorChar.ToString()))
    {
        return path + Path.DirectorySeparatorChar;
    }

    return path;
}

Risposta di interoperabilità di Windows

Esiste un'API di Windows denominata PathRelativePathToA che può essere utilizzata per trovare un percorso relativo. Si noti che i percorsi di file o directory passati alla funzione devono esistere affinché funzioni.

var relativePath = PathExtended.GetRelativePath(
    @"C:\Program Files\Dummy Folder\MyProgram",
    @"C:\Program Files\Dummy Folder\MyProgram\Data\datafile1.dat");

public static class PathExtended
{
    private const int FILE_ATTRIBUTE_DIRECTORY = 0x10;
    private const int FILE_ATTRIBUTE_NORMAL = 0x80;
    private const int MaximumPath = 260;

    public static string GetRelativePath(string fromPath, string toPath)
    {
        var fromAttribute = GetPathAttribute(fromPath);
        var toAttribute = GetPathAttribute(toPath);

        var stringBuilder = new StringBuilder(MaximumPath);
        if (PathRelativePathTo(
            stringBuilder,
            fromPath,
            fromAttribute,
            toPath,
            toAttribute) == 0)
        {
            throw new ArgumentException("Paths must have a common prefix.");
        }

        return stringBuilder.ToString();
    }

    private static int GetPathAttribute(string path)
    {
        var directory = new DirectoryInfo(path);
        if (directory.Exists)
        {
            return FILE_ATTRIBUTE_DIRECTORY;
        }

        var file = new FileInfo(path);
        if (file.Exists)
        {
            return FILE_ATTRIBUTE_NORMAL;
        }

        throw new FileNotFoundException(
            "A file or directory with the specified path was not found.",
            path);
    }

    [DllImport("shlwapi.dll", SetLastError = true)]
    private static extern int PathRelativePathTo(
        StringBuilder pszPath,
        string pszFrom,
        int dwAttrFrom,
        string pszTo,
        int dwAttrTo);
}

Esiste una funzione Win32 (C ++) in shlwapi.dll che fa esattamente quello che vuoi: PathRelativePathTo()

Tuttavia, non sono a conoscenza di alcun modo per accedervi da .NET se non per P / Invoke.

Se si utilizza .NET Core 2.0,Path.GetRelativePath() è disponibile fornendo questa funzionalità specifica:

        var relativeTo = @"C:\Program Files\Dummy Folder\MyProgram";
        var path = @"C:\Program Files\Dummy Folder\MyProgram\Data\datafile1.dat";

        string relativePath = System.IO.Path.GetRelativePath(relativeTo, path);

        System.Console.WriteLine(relativePath);
        // output --> Data\datafile1.dat 

Altrimenti, per .NET framework completo (a partire dalla v4.7) consigliamo di utilizzare una delle altre risposte suggerite.

L'ho usato in passato.

/// <summary>
/// Creates a relative path from one file
/// or folder to another.
/// </summary>
/// <param name="fromDirectory">
/// Contains the directory that defines the
/// start of the relative path.
/// </param>
/// <param name="toPath">
/// Contains the path that defines the
/// endpoint of the relative path.
/// </param>
/// <returns>
/// The relative path from the start
/// directory to the end path.
/// </returns>
/// <exception cref="ArgumentNullException"></exception>
public static string MakeRelative(string fromDirectory, string toPath)
{
  if (fromDirectory == null)
    throw new ArgumentNullException("fromDirectory");

  if (toPath == null)
    throw new ArgumentNullException("toPath");

  bool isRooted = (Path.IsPathRooted(fromDirectory) && Path.IsPathRooted(toPath));

  if (isRooted)
  {
    bool isDifferentRoot = (string.Compare(Path.GetPathRoot(fromDirectory), Path.GetPathRoot(toPath), true) != 0);

    if (isDifferentRoot)
      return toPath;
  }

  List<string> relativePath = new List<string>();
  string[] fromDirectories = fromDirectory.Split(Path.DirectorySeparatorChar);

  string[] toDirectories = toPath.Split(Path.DirectorySeparatorChar);

  int length = Math.Min(fromDirectories.Length, toDirectories.Length);

  int lastCommonRoot = -1;

  // find common root
  for (int x = 0; x < length; x++)
  {
    if (string.Compare(fromDirectories[x], toDirectories[x], true) != 0)
      break;

    lastCommonRoot = x;
  }

  if (lastCommonRoot == -1)
    return toPath;

  // add relative folders in from path
  for (int x = lastCommonRoot + 1; x < fromDirectories.Length; x++)
  {
    if (fromDirectories[x].Length > 0)
      relativePath.Add("..");
  }

  // add to folders to path
  for (int x = lastCommonRoot + 1; x < toDirectories.Length; x++)
  {
    relativePath.Add(toDirectories[x]);
  }

  // create relative path
  string[] relativeParts = new string[relativePath.Count];
  relativePath.CopyTo(relativeParts, 0);

  string newPath = string.Join(Path.DirectorySeparatorChar.ToString(), relativeParts);

  return newPath;
}

Come sottolinea Alex Brault, soprattutto su Windows, il percorso assoluto (con lettera di unità e tutto) è inequivocabile e spesso migliore.

OpenFileDialog non dovrebbe usare una normale struttura ad albero del browser?

Per ottenere una certa nomenclatura, RefDir è la directory relativa alla quale si desidera specificare il percorso; l'AbsName è il nome del percorso assoluto che si desidera mappare; e RelPath è il percorso relativo risultante.

Prendi la prima di queste opzioni che corrispondono:

• Se si dispone di lettere di unità diverse, non esiste un percorso relativo da RefDir a AbsName; devi usare AbsName.
• Se AbsName si trova in una sottodirectory di RefDir o è un file all'interno di RefDir, è sufficiente rimuovere RefDir dall'inizio di AbsName per creare RelPath; opzionalmente anteporre "./" (o ". \" poiché sei su Windows).
• Trova il prefisso comune più lungo di RefDir e AbsName (dove D: \ Abc \ Def e D: \ Abc \ Default condividono D: \ Abc come prefisso comune più lungo; deve essere una mappatura dei componenti del nome, non un semplice comune più lungo sottostringa); chiamalo LCP. Rimuovere LCP da AbsName e RefDir. Per ogni componente del percorso lasciato in (RefDir - LCP), anteporre ".. \" a (AbsName - LCP) per produrre RelPath.

Per illustrare l'ultima regola (che è, ovviamente, di gran lunga la più complessa), inizia con:

RefDir = D:\Abc\Def\Ghi
AbsName = D:\Abc\Default\Karma\Crucible

Poi

LCP = D:\Abc
(RefDir - LCP) = Def\Ghi
(Absname - LCP) = Default\Karma\Crucible
RelPath = ..\..\Default\Karma\Crucible

Mentre scrivevo, DavidK ha prodotto una risposta che suggerisce che non sei il primo ad aver bisogno di questa funzione e che esiste una funzione standard per fare questo lavoro. Usalo Ma non c'è nulla di male nel riuscire a pensare ai tuoi primi principi.

Ad eccezione del fatto che i sistemi Unix non supportano le lettere di unità (quindi tutto si trova sempre nella stessa directory principale e pertanto il primo punto elenco è irrilevante), la stessa tecnica potrebbe essere utilizzata su Unix.

È molto lontano, ma la classe System.Uri ha un metodo chiamato MakeRelativeUri. Forse potresti usarlo. È un peccato che System.IO.Path non abbia questo.

Come indicato sopra, .NET Core 2.x ha implementatoPath.GetRelativePath .

Il codice seguente è adattato da fonti e funziona perfettamente con .NET 4.7.1 Framework.

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

//Adapted from https://github.com/dotnet/corefx/blob/master/src/Common/src/CoreLib/System/IO/Path.cs#L697
// by Anton Krouglov

using System.Runtime.CompilerServices;
using System.Diagnostics;
using System.Text;
using Xunit;

namespace System.IO {
    // Provides methods for processing file system strings in a cross-platform manner.
    // Most of the methods don't do a complete parsing (such as examining a UNC hostname), 
    // but they will handle most string operations.
    public static class PathNetCore {

        /// <summary>
        /// Create a relative path from one path to another. Paths will be resolved before calculating the difference.
        /// Default path comparison for the active platform will be used (OrdinalIgnoreCase for Windows or Mac, Ordinal for Unix).
        /// </summary>
        /// <param name="relativeTo">The source path the output should be relative to. This path is always considered to be a directory.</param>
        /// <param name="path">The destination path.</param>
        /// <returns>The relative path or <paramref name="path"/> if the paths don't share the same root.</returns>
        /// <exception cref="ArgumentNullException">Thrown if <paramref name="relativeTo"/> or <paramref name="path"/> is <c>null</c> or an empty string.</exception>
        public static string GetRelativePath(string relativeTo, string path) {
            return GetRelativePath(relativeTo, path, StringComparison);
        }

        private static string GetRelativePath(string relativeTo, string path, StringComparison comparisonType) {
            if (string.IsNullOrEmpty(relativeTo)) throw new ArgumentNullException(nameof(relativeTo));
            if (string.IsNullOrEmpty(path)) throw new ArgumentNullException(nameof(path));
            Debug.Assert(comparisonType == StringComparison.Ordinal ||
                         comparisonType == StringComparison.OrdinalIgnoreCase);

            relativeTo = Path.GetFullPath(relativeTo);
            path = Path.GetFullPath(path);

            // Need to check if the roots are different- if they are we need to return the "to" path.
            if (!PathInternalNetCore.AreRootsEqual(relativeTo, path, comparisonType))
                return path;

            int commonLength = PathInternalNetCore.GetCommonPathLength(relativeTo, path,
                ignoreCase: comparisonType == StringComparison.OrdinalIgnoreCase);

            // If there is nothing in common they can't share the same root, return the "to" path as is.
            if (commonLength == 0)
                return path;

            // Trailing separators aren't significant for comparison
            int relativeToLength = relativeTo.Length;
            if (PathInternalNetCore.EndsInDirectorySeparator(relativeTo))
                relativeToLength--;

            bool pathEndsInSeparator = PathInternalNetCore.EndsInDirectorySeparator(path);
            int pathLength = path.Length;
            if (pathEndsInSeparator)
                pathLength--;

            // If we have effectively the same path, return "."
            if (relativeToLength == pathLength && commonLength >= relativeToLength) return ".";

            // We have the same root, we need to calculate the difference now using the
            // common Length and Segment count past the length.
            //
            // Some examples:
            //
            //  C:\Foo C:\Bar L3, S1 -> ..\Bar
            //  C:\Foo C:\Foo\Bar L6, S0 -> Bar
            //  C:\Foo\Bar C:\Bar\Bar L3, S2 -> ..\..\Bar\Bar
            //  C:\Foo\Foo C:\Foo\Bar L7, S1 -> ..\Bar

            StringBuilder
                sb = new StringBuilder(); //StringBuilderCache.Acquire(Math.Max(relativeTo.Length, path.Length));

            // Add parent segments for segments past the common on the "from" path
            if (commonLength < relativeToLength) {
                sb.Append("..");

                for (int i = commonLength + 1; i < relativeToLength; i++) {
                    if (PathInternalNetCore.IsDirectorySeparator(relativeTo[i])) {
                        sb.Append(DirectorySeparatorChar);
                        sb.Append("..");
                    }
                }
            }
            else if (PathInternalNetCore.IsDirectorySeparator(path[commonLength])) {
                // No parent segments and we need to eat the initial separator
                //  (C:\Foo C:\Foo\Bar case)
                commonLength++;
            }

            // Now add the rest of the "to" path, adding back the trailing separator
            int differenceLength = pathLength - commonLength;
            if (pathEndsInSeparator)
                differenceLength++;

            if (differenceLength > 0) {
                if (sb.Length > 0) {
                    sb.Append(DirectorySeparatorChar);
                }

                sb.Append(path, commonLength, differenceLength);
            }

            return sb.ToString(); //StringBuilderCache.GetStringAndRelease(sb);
        }

        // Public static readonly variant of the separators. The Path implementation itself is using
        // internal const variant of the separators for better performance.
        public static readonly char DirectorySeparatorChar = PathInternalNetCore.DirectorySeparatorChar;
        public static readonly char AltDirectorySeparatorChar = PathInternalNetCore.AltDirectorySeparatorChar;
        public static readonly char VolumeSeparatorChar = PathInternalNetCore.VolumeSeparatorChar;
        public static readonly char PathSeparator = PathInternalNetCore.PathSeparator;

        /// <summary>Returns a comparison that can be used to compare file and directory names for equality.</summary>
        internal static StringComparison StringComparison => StringComparison.OrdinalIgnoreCase;
    }

    /// <summary>Contains internal path helpers that are shared between many projects.</summary>
    internal static class PathInternalNetCore {
        internal const char DirectorySeparatorChar = '\\';
        internal const char AltDirectorySeparatorChar = '/';
        internal const char VolumeSeparatorChar = ':';
        internal const char PathSeparator = ';';

        internal const string ExtendedDevicePathPrefix = @"\\?\";
        internal const string UncPathPrefix = @"\\";
        internal const string UncDevicePrefixToInsert = @"?\UNC\";
        internal const string UncExtendedPathPrefix = @"\\?\UNC\";
        internal const string DevicePathPrefix = @"\\.\";

        //internal const int MaxShortPath = 260;

        // \\?\, \\.\, \??\
        internal const int DevicePrefixLength = 4;

        /// <summary>
        /// Returns true if the two paths have the same root
        /// </summary>
        internal static bool AreRootsEqual(string first, string second, StringComparison comparisonType) {
            int firstRootLength = GetRootLength(first);
            int secondRootLength = GetRootLength(second);

            return firstRootLength == secondRootLength
                   && string.Compare(
                       strA: first,
                       indexA: 0,
                       strB: second,
                       indexB: 0,
                       length: firstRootLength,
                       comparisonType: comparisonType) == 0;
        }

        /// <summary>
        /// Gets the length of the root of the path (drive, share, etc.).
        /// </summary>
        internal static int GetRootLength(string path) {
            int i = 0;
            int volumeSeparatorLength = 2; // Length to the colon "C:"
            int uncRootLength = 2; // Length to the start of the server name "\\"

            bool extendedSyntax = path.StartsWith(ExtendedDevicePathPrefix);
            bool extendedUncSyntax = path.StartsWith(UncExtendedPathPrefix);
            if (extendedSyntax) {
                // Shift the position we look for the root from to account for the extended prefix
                if (extendedUncSyntax) {
                    // "\\" -> "\\?\UNC\"
                    uncRootLength = UncExtendedPathPrefix.Length;
                }
                else {
                    // "C:" -> "\\?\C:"
                    volumeSeparatorLength += ExtendedDevicePathPrefix.Length;
                }
            }

            if ((!extendedSyntax || extendedUncSyntax) && path.Length > 0 && IsDirectorySeparator(path[0])) {
                // UNC or simple rooted path (e.g. "\foo", NOT "\\?\C:\foo")

                i = 1; //  Drive rooted (\foo) is one character
                if (extendedUncSyntax || (path.Length > 1 && IsDirectorySeparator(path[1]))) {
                    // UNC (\\?\UNC\ or \\), scan past the next two directory separators at most
                    // (e.g. to \\?\UNC\Server\Share or \\Server\Share\)
                    i = uncRootLength;
                    int n = 2; // Maximum separators to skip
                    while (i < path.Length && (!IsDirectorySeparator(path[i]) || --n > 0)) i++;
                }
            }
            else if (path.Length >= volumeSeparatorLength &&
                     path[volumeSeparatorLength - 1] == PathNetCore.VolumeSeparatorChar) {
                // Path is at least longer than where we expect a colon, and has a colon (\\?\A:, A:)
                // If the colon is followed by a directory separator, move past it
                i = volumeSeparatorLength;
                if (path.Length >= volumeSeparatorLength + 1 && IsDirectorySeparator(path[volumeSeparatorLength])) i++;
            }

            return i;
        }

        /// <summary>
        /// True if the given character is a directory separator.
        /// </summary>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal static bool IsDirectorySeparator(char c) {
            return c == PathNetCore.DirectorySeparatorChar || c == PathNetCore.AltDirectorySeparatorChar;
        }

        /// <summary>
        /// Get the common path length from the start of the string.
        /// </summary>
        internal static int GetCommonPathLength(string first, string second, bool ignoreCase) {
            int commonChars = EqualStartingCharacterCount(first, second, ignoreCase: ignoreCase);

            // If nothing matches
            if (commonChars == 0)
                return commonChars;

            // Or we're a full string and equal length or match to a separator
            if (commonChars == first.Length
                && (commonChars == second.Length || IsDirectorySeparator(second[commonChars])))
                return commonChars;

            if (commonChars == second.Length && IsDirectorySeparator(first[commonChars]))
                return commonChars;

            // It's possible we matched somewhere in the middle of a segment e.g. C:\Foodie and C:\Foobar.
            while (commonChars > 0 && !IsDirectorySeparator(first[commonChars - 1]))
                commonChars--;

            return commonChars;
        }

        /// <summary>
        /// Gets the count of common characters from the left optionally ignoring case
        /// </summary>
        internal static unsafe int EqualStartingCharacterCount(string first, string second, bool ignoreCase) {
            if (string.IsNullOrEmpty(first) || string.IsNullOrEmpty(second)) return 0;

            int commonChars = 0;

            fixed (char* f = first)
            fixed (char* s = second) {
                char* l = f;
                char* r = s;
                char* leftEnd = l + first.Length;
                char* rightEnd = r + second.Length;

                while (l != leftEnd && r != rightEnd
                                    && (*l == *r || (ignoreCase &&
                                                     char.ToUpperInvariant((*l)) == char.ToUpperInvariant((*r))))) {
                    commonChars++;
                    l++;
                    r++;
                }
            }

            return commonChars;
        }

        /// <summary>
        /// Returns true if the path ends in a directory separator.
        /// </summary>
        internal static bool EndsInDirectorySeparator(string path)
            => path.Length > 0 && IsDirectorySeparator(path[path.Length - 1]);
    }

    /// <summary> Tests for PathNetCore.GetRelativePath </summary>
    public static class GetRelativePathTests {
        [Theory]
        [InlineData(@"C:\", @"C:\", @".")]
        [InlineData(@"C:\a", @"C:\a\", @".")]
        [InlineData(@"C:\A", @"C:\a\", @".")]
        [InlineData(@"C:\a\", @"C:\a", @".")]
        [InlineData(@"C:\", @"C:\b", @"b")]
        [InlineData(@"C:\a", @"C:\b", @"..\b")]
        [InlineData(@"C:\a", @"C:\b\", @"..\b\")]
        [InlineData(@"C:\a\b", @"C:\a", @"..")]
        [InlineData(@"C:\a\b", @"C:\a\", @"..")]
        [InlineData(@"C:\a\b\", @"C:\a", @"..")]
        [InlineData(@"C:\a\b\", @"C:\a\", @"..")]
        [InlineData(@"C:\a\b\c", @"C:\a\b", @"..")]
        [InlineData(@"C:\a\b\c", @"C:\a\b\", @"..")]
        [InlineData(@"C:\a\b\c", @"C:\a", @"..\..")]
        [InlineData(@"C:\a\b\c", @"C:\a\", @"..\..")]
        [InlineData(@"C:\a\b\c\", @"C:\a\b", @"..")]
        [InlineData(@"C:\a\b\c\", @"C:\a\b\", @"..")]
        [InlineData(@"C:\a\b\c\", @"C:\a", @"..\..")]
        [InlineData(@"C:\a\b\c\", @"C:\a\", @"..\..")]
        [InlineData(@"C:\a\", @"C:\b", @"..\b")]
        [InlineData(@"C:\a", @"C:\a\b", @"b")]
        [InlineData(@"C:\a", @"C:\A\b", @"b")]
        [InlineData(@"C:\a", @"C:\b\c", @"..\b\c")]
        [InlineData(@"C:\a\", @"C:\a\b", @"b")]
        [InlineData(@"C:\", @"D:\", @"D:\")]
        [InlineData(@"C:\", @"D:\b", @"D:\b")]
        [InlineData(@"C:\", @"D:\b\", @"D:\b\")]
        [InlineData(@"C:\a", @"D:\b", @"D:\b")]
        [InlineData(@"C:\a\", @"D:\b", @"D:\b")]
        [InlineData(@"C:\ab", @"C:\a", @"..\a")]
        [InlineData(@"C:\a", @"C:\ab", @"..\ab")]
        [InlineData(@"C:\", @"\\LOCALHOST\Share\b", @"\\LOCALHOST\Share\b")]
        [InlineData(@"\\LOCALHOST\Share\a", @"\\LOCALHOST\Share\b", @"..\b")]
        //[PlatformSpecific(TestPlatforms.Windows)]  // Tests Windows-specific paths
        public static void GetRelativePath_Windows(string relativeTo, string path, string expected) {
            string result = PathNetCore.GetRelativePath(relativeTo, path);
            Assert.Equal(expected, result);

            // Check that we get the equivalent path when the result is combined with the sources
            Assert.Equal(
                Path.GetFullPath(path).TrimEnd(Path.DirectorySeparatorChar),
                Path.GetFullPath(Path.Combine(Path.GetFullPath(relativeTo), result))
                    .TrimEnd(Path.DirectorySeparatorChar),
                ignoreCase: true,
                ignoreLineEndingDifferences: false,
                ignoreWhiteSpaceDifferences: false);
        }
    }
}

Sto usando questo:

public static class StringExtensions
{
  /// <summary>
  /// Creates a relative path from one file or folder to another.
  /// </summary>
  /// <param name="absPath">Absolute path.</param>
  /// <param name="relTo">Directory that defines the start of the relative path.</param> 
  /// <returns>The relative path from the start directory to the end path.</returns>
  public static string MakeRelativePath(this string absPath, string relTo)
  {
      string[] absParts = absPath.Split(Path.DirectorySeparatorChar);
      string[] relParts = relTo.Split(Path.DirectorySeparatorChar);

      // Get the shortest of the two paths
      int len = absParts.Length < relParts.Length
          ? absParts.Length : relParts.Length;

      // Use to determine where in the loop we exited
      int lastCommonRoot = -1;
      int index;

      // Find common root
      for (index = 0; index < len; index++)
      {
          if (absParts[index].Equals(relParts[index], StringComparison.OrdinalIgnoreCase))
              lastCommonRoot = index;
          else 
            break;
      }

      // If we didn't find a common prefix then throw
      if (lastCommonRoot == -1)
          throw new ArgumentException("The path of the two files doesn't have any common base.");

      // Build up the relative path
      var relativePath = new StringBuilder();

      // Add on the ..
      for (index = lastCommonRoot + 1; index < relParts.Length; index++)
      {
        relativePath.Append("..");
        relativePath.Append(Path.DirectorySeparatorChar);
      }

      // Add on the folders
      for (index = lastCommonRoot + 1; index < absParts.Length - 1; index++)
      {
        relativePath.Append(absParts[index]);
        relativePath.Append(Path.DirectorySeparatorChar);
      }
      relativePath.Append(absParts[absParts.Length - 1]);

      return relativePath.ToString();
  }
}

Uso:

RelPath = AbsPath.Replace(ApplicationPath, ".")

Se sei sicuro che il tuo percorso assoluto 2 sia sempre relativo al percorso assoluto, rimuovi solo i primi N caratteri dal percorso2, dove N è la lunghezza del percorso1.

Vuoi usare il CommonPathmetodo di questa RelativePathclasse. Una volta che hai il percorso comune, è sufficiente rimuoverlo dal percorso che si desidera visualizzare.

Namespace IO.Path

    Public NotInheritable Class RelativePath

        Private Declare Function PathRelativePathTo Lib "shlwapi" Alias "PathRelativePathToA" ( _
            ByVal pszPath As String, _
            ByVal pszFrom As String, _
            ByVal dwAttrFrom As Integer, _
            ByVal pszTo As String, _
            ByVal dwAttrTo As Integer) As Integer

        Private Declare Function PathCanonicalize Lib "shlwapi" Alias "PathCanonicalizeA" ( _
            ByVal pszBuf As String, _
            ByVal pszPath As String) As Integer

        Private Const FILE_ATTRIBUTE_DIRECTORY As Short = &H10S

        Private Const MAX_PATH As Short = 260

        Private _path As String
        Private _isDirectory As Boolean

#Region " Constructors "

        Public Sub New()

        End Sub

        Public Sub New(ByVal path As String)
            _path = path
        End Sub

        Public Sub New(ByVal path As String, ByVal isDirectory As Boolean)
            _path = path
            _isDirectory = isDirectory
        End Sub

#End Region

        Private Shared Function StripNulls(ByVal value As String) As String
            StripNulls = value
            If (InStr(value, vbNullChar) > 0) Then
                StripNulls = Left(value, InStr(value, vbNullChar) - 1)
            End If
        End Function

        Private Shared Function TrimCurrentDirectory(ByVal path As String) As String
            TrimCurrentDirectory = path
            If Len(path) >= 2 And Left(path, 2) = ".\" Then
                TrimCurrentDirectory = Mid(path, 3)
            End If
        End Function

        ''' <summary>
        ''' 3. conforming to general principles: conforming to accepted principles or standard practice
        ''' </summary>
        Public Shared Function Canonicalize(ByVal path As String) As String
            Dim sPath As String

            sPath = New String(Chr(0), MAX_PATH)

            If PathCanonicalize(sPath, path) = 0 Then
                Canonicalize = vbNullString
            Else
                Canonicalize = StripNulls(sPath)
            End If

        End Function

        ''' <summary>
        ''' Returns the most common path between two paths.
        ''' </summary>
        ''' <remarks>
        ''' <para>returns the path that is common between two paths</para>
        ''' <para>c:\FolderA\FolderB\FolderC</para>
        '''   c:\FolderA\FolderD\FolderE\File.Ext
        ''' 
        '''   results in:
        '''       c:\FolderA\
        ''' </remarks>
        Public Shared Function CommonPath(ByVal path1 As String, ByVal path2 As String) As String
            'returns the path that is common between two paths
            '
            '   c:\FolderA\FolderB\FolderC
            '   c:\FolderA\FolderD\FolderE\File.Ext
            '
            '   results in:
            '       c:\FolderA\

            Dim sResult As String = String.Empty
            Dim iPos1, iPos2 As Integer
            path1 = Canonicalize(path1)
            path2 = Canonicalize(path2)
            Do
                If Left(path1, iPos1) = Left(path2, iPos2) Then
                    sResult = Left(path1, iPos1)
                End If
                iPos1 = InStr(iPos1 + 1, path1, "\")
                iPos2 = InStr(iPos2 + 1, path1, "\")
            Loop While Left(path1, iPos1) = Left(path2, iPos2)

            Return sResult

        End Function

        Public Function CommonPath(ByVal path As String) As String
            Return CommonPath(_path, path)
        End Function

        Public Shared Function RelativePathTo(ByVal source As String, ByVal isSourceDirectory As Boolean, ByVal target As String, ByVal isTargetDirectory As Boolean) As String
            'DEVLIB
            '   05/23/05  1:47PM - Fixed call to PathRelativePathTo, iTargetAttribute is now passed to dwAttrTo instead of IsTargetDirectory.
            '       For Visual Basic 6.0, the fix does not change testing results,
            '           because when the Boolean IsTargetDirectory is converted to the Long dwAttrTo it happens to contain FILE_ATTRIBUTE_DIRECTORY,
            '
            Dim sRelativePath As String
            Dim iSourceAttribute, iTargetAttribute As Integer

            sRelativePath = New String(Chr(0), MAX_PATH)
            source = Canonicalize(source)
            target = Canonicalize(target)

            If isSourceDirectory Then
                iSourceAttribute = FILE_ATTRIBUTE_DIRECTORY
            End If

            If isTargetDirectory Then
                iTargetAttribute = FILE_ATTRIBUTE_DIRECTORY
            End If

            If PathRelativePathTo(sRelativePath, source, iSourceAttribute, target, iTargetAttribute) = 0 Then
                RelativePathTo = vbNullString
            Else
                RelativePathTo = TrimCurrentDirectory(StripNulls(sRelativePath))
            End If

        End Function

        Public Function RelativePath(ByVal target As String) As String
            Return RelativePathTo(_path, _isDirectory, target, False)
        End Function

    End Class

End Namespace

Dividerei entrambi i tuoi percorsi a livello di directory. Da lì, trova il punto di divergenza e torna alla cartella dell'assembly, anteponendo un '../' ogni volta che passi una directory.

Tieni presente, tuttavia, che un percorso assoluto funziona ovunque ed è generalmente più facile da leggere di un percorso relativo. Personalmente non mostrerei a un utente un percorso relativo se non fosse assolutamente necessario.

Se sai che toPath è contenuto da fromPath, puoi mantenerlo semplice. Lascio fuori le affermazioni per brevità.

public static string MakeRelativePath(string fromPath, string toPath)
{
    // use Path.GetFullPath to canonicalise the paths (deal with multiple directory seperators, etc)
    return Path.GetFullPath(toPath).Substring(Path.GetFullPath(fromPath).Length + 1);
}

La funzione che utilizza l'URI ha restituito un percorso relativo "quasi". Comprendeva una directory che contiene direttamente il file quale percorso relativo volevo ottenere.

Qualche tempo fa ho scritto una semplice funzione che restituisce il percorso relativo della cartella o del file e anche se si trova su un'altra unità, include anche la lettera dell'unità.

Per favore dai un'occhiata:

    public static string GetRelativePath(string BasePath, string AbsolutePath)
    {
        char Separator = Path.DirectorySeparatorChar;
        if (string.IsNullOrWhiteSpace(BasePath)) BasePath = Directory.GetCurrentDirectory();
        var ReturnPath = "";
        var CommonPart = "";
        var BasePathFolders = BasePath.Split(Separator);
        var AbsolutePathFolders = AbsolutePath.Split(Separator);
        var i = 0;
        while (i < BasePathFolders.Length & i < AbsolutePathFolders.Length)
        {
            if (BasePathFolders[i].ToLower() == AbsolutePathFolders[i].ToLower())
            {
                CommonPart += BasePathFolders[i] + Separator;
            }
            else
            {
                break;
            }
            i += 1;
        }
        if (CommonPart.Length > 0)
        {
            var parents = BasePath.Substring(CommonPart.Length - 1).Split(Separator);
            foreach (var ParentDir in parents)
            {
                if (!string.IsNullOrEmpty(ParentDir))
                    ReturnPath += ".." + Separator;
            }
        }
        ReturnPath += AbsolutePath.Substring(CommonPart.Length);
        return ReturnPath;
    }

Se hai una casella di testo di sola lettura, non potresti non renderla un'etichetta e impostare AutoEllipsis = true?

in alternativa ci sono post con codice per generare autonomamente l'autoellipsis: (questo lo fa per una griglia, dovresti invece passare la larghezza della casella di testo. Non è giusto in quanto si taglia un po 'più del necessario e non ho avuto modo di scoprire dove il calcolo non è corretto. Sarebbe abbastanza facile modificarlo per rimuovere la prima parte della directory anziché l'ultima se lo desideri.

Private Function AddEllipsisPath(ByVal text As String, ByVal colIndex As Integer, ByVal grid As DataGridView) As String
    'Get the size with the column's width 
    Dim colWidth As Integer = grid.Columns(colIndex).Width

    'Calculate the dimensions of the text with the current font
    Dim textSize As SizeF = MeasureString(text, grid.Font)

    Dim rawText As String = text
    Dim FileNameLen As Integer = text.Length - text.LastIndexOf("\")
    Dim ReplaceWith As String = "\..."

    Do While textSize.Width > colWidth
        ' Trim to make room for the ellipsis
        Dim LastFolder As Integer = rawText.LastIndexOf("\", rawText.Length - FileNameLen - 1)

        If LastFolder < 0 Then
            Exit Do
        End If

        rawText = rawText.Substring(0, LastFolder) + ReplaceWith + rawText.Substring(rawText.Length - FileNameLen)

        If ReplaceWith.Length > 0 Then
            FileNameLen += 4
            ReplaceWith = ""
        End If
        textSize = MeasureString(rawText, grid.Font)
    Loop

    Return rawText
End Function

Private Function MeasureString(ByVal text As String, ByVal fontInfo As Font) As SizeF
    Dim size As SizeF
    Dim emSize As Single = fontInfo.Size
    If emSize = 0 Then emSize = 12

    Dim stringFont As New Font(fontInfo.Name, emSize)

    Dim bmp As New Bitmap(1000, 100)
    Dim g As Graphics = Graphics.FromImage(bmp)

    size = g.MeasureString(text, stringFont)
    g.Dispose()
    Return size
End Function

    public static string ToRelativePath(string filePath, string refPath)
    {
        var pathNormalized = Path.GetFullPath(filePath);

        var refNormalized = Path.GetFullPath(refPath);
        refNormalized = refNormalized.TrimEnd('\\', '/');

        if (!pathNormalized.StartsWith(refNormalized))
            throw new ArgumentException();
        var res = pathNormalized.Substring(refNormalized.Length + 1);
        return res;
    }

Questo dovrebbe funzionare:

private string rel(string path) {
  string[] cwd  = new Regex(@"[\\]").Split(Directory.GetCurrentDirectory());
  string[] fp   = new Regex(@"[\\]").Split(path);

  int common = 0;

  for (int n = 0; n < fp.Length; n++) {
    if (n < cwd.Length && n < fp.Length && cwd[n] == fp[n]) {
      common++;
    }
  }

  if (common > 0) {
    List<string> rp = new List<string>();

    for (int n = 0; n < (cwd.Length - common); n++) {
      rp.Add("..");
    }

    for (int n = common; n < fp.Length; n++) {
      rp.Add(fp[n]);
    }

    return String.Join("/", rp.ToArray());
  } else {
    return String.Join("/", fp);
  }
}

Il modo con Uri non ha funzionato su sistemi linux / macOS. Il percorso '/ var / www / root' non può essere convertito in Uri. Modo più universale: fai tutto a mano.

public static string MakeRelativePath(string fromPath, string toPath, string sep = "/")
{
    var fromParts = fromPath.Split(new[] { '/', '\\'},
        StringSplitOptions.RemoveEmptyEntries);
    var toParts = toPath.Split(new[] { '/', '\\'},
        StringSplitOptions.RemoveEmptyEntries);

    var matchedParts = fromParts
        .Zip(toParts, (x, y) => string.Compare(x, y, true) == 0)
        .TakeWhile(x => x).Count();

    return string.Join("", Enumerable.Range(0, fromParts.Length - matchedParts)
        .Select(x => ".." + sep)) +
            string.Join(sep, toParts.Skip(matchedParts));
}        

PS: uso "/" come valore predefinito di separatore anziché Path.DirectorySeparatorChar, perché il risultato di questo metodo è stato utilizzato come uri nella mia app.

ecco il mio:

public static string RelativePathTo(this System.IO.DirectoryInfo @this, string to)
{
    var rgFrom = @this.FullName.Split(new[] { Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar }, StringSplitOptions.RemoveEmptyEntries);
    var rgTo = to.Split(new[] { Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar }, StringSplitOptions.RemoveEmptyEntries);
    var cSame = rgFrom.TakeWhile((p, i) => i < rgTo.Length && string.Equals(p, rgTo[i])).Count();

    return Path.Combine(
        Enumerable.Range(0, rgFrom.Length - cSame)
        .Select(_ => "..")
        .Concat(rgTo.Skip(cSame))
        .ToArray()
    );
}

Gioca con qualcosa del tipo:

private String GetRelativePath(Int32 level, String directory, out String errorMessage) {
        if (level < 0 || level > 5) {
            errorMessage = "Find some more smart input data";
            return String.Empty;
        }
        // ==========================
        while (level != 0) {
            directory = Path.GetDirectoryName(directory);
            level -= 1;
        }
        // ==========================
        errorMessage = String.Empty;
        return directory;
    }

E provalo

[Test]
    public void RelativeDirectoryPathTest() {
        var relativePath =
            GetRelativePath(3, AppDomain.CurrentDomain.BaseDirectory, out var errorMessage);
        Console.WriteLine(relativePath);
        if (String.IsNullOrEmpty(errorMessage) == false) {
            Console.WriteLine(errorMessage);
            Assert.Fail("Can not find relative path");
        }
    }

In ASP.NET Core 2, se si desidera il percorso relativo bin\Debug\netcoreapp2.2è possibile utilizzare la seguente combinazione:

using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
public class RenderingService : IRenderingService
{

    private readonly IHostingEnvironment _hostingEnvironment;
    public RenderingService(IHostingEnvironment hostingEnvironment)
    {
    _hostingEnvironment = hostingEnvironment;
    }

    public string RelativeAssemblyDirectory()
    {
        var contentRootPath = _hostingEnvironment.ContentRootPath;
        string executingAssemblyDirectoryAbsolutePath = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location);
        string executingAssemblyDirectoryRelativePath = System.IO.Path.GetRelativePath(contentRootPath, executingAssemblyDirectoryAbsolutePath);
        return executingAssemblyDirectoryRelativePath;
    }
}