获取相对于当前工作目录的路径？ [复制]

Question

我正在编写一个控制台实用程序来对命令行中指定的文件进行一些处理，但我遇到了一个无法通过 Google/Stack Overflow 解决的问题。如果指定了完整路径（包括驱动器号），如何重新格式化该路径以相对于当前工作目录？

一定有类似于 VirtualPathUtility.MakeRelative 函数的东西，但如果有的话，我会忽略它。

Answer 1

如果你不介意切换斜线，你可以[ab]使用Uri：

Uri file = new Uri(@"c:\foo\bar\blop\blap.txt");
// Must end in a slash to indicate folder
Uri folder = new Uri(@"c:\foo\bar\");
string relativePath = 
Uri.UnescapeDataString(
    folder.MakeRelativeUri(file)
        .ToString()
        .Replace('/', Path.DirectorySeparatorChar)
    );

作为一个函数/方法：

string GetRelativePath(string filespec, string folder)
{
    Uri pathUri = new Uri(filespec);
    // Folders must end in a slash
    if (!folder.EndsWith(Path.DirectorySeparatorChar.ToString()))
    {
        folder += Path.DirectorySeparatorChar;
    }
    Uri folderUri = new Uri(folder);
    return Uri.UnescapeDataString(folderUri.MakeRelativeUri(pathUri).ToString().Replace('/', Path.DirectorySeparatorChar));
}

Answer 2

您可以使用Environment.CurrentDirectory 获取当前目录，使用FileSystemInfo.FullPath 获取任何位置的完整路径。因此，完全限定当前目录和相关文件，然后检查完​​整文件名是否以目录名开头 - 如果是，则根据目录名的长度取适当的子字符串。

这里有一些示例代码：

using System;
using System.IO;

class Program
{
    public static void Main(string[] args)
    {
        string currentDir = Environment.CurrentDirectory;
        DirectoryInfo directory = new DirectoryInfo(currentDir);
        FileInfo file = new FileInfo(args[0]);

        string fullDirectory = directory.FullName;
        string fullFile = file.FullName;

        if (!fullFile.StartsWith(fullDirectory))
        {
            Console.WriteLine("Unable to make relative path");
        }
        else
        {
            // The +1 is to avoid the directory separator
            Console.WriteLine("Relative path: {0}",
                              fullFile.Substring(fullDirectory.Length+1));
        }
    }
}

我并不是说它是世界上最强大的东西（符号链接可能会混淆它），但如果这只是你偶尔使用的工具，那可能没问题。

Answer 3

public string MakeRelativePath(string workingDirectory, string fullPath)
{
    string result = string.Empty;
    int offset;

    // this is the easy case.  The file is inside of the working directory.
    if( fullPath.StartsWith(workingDirectory) )
    {
        return fullPath.Substring(workingDirectory.Length + 1);
    }

    // the hard case has to back out of the working directory
    string[] baseDirs = workingDirectory.Split(new char[] { ':', '\\', '/' });
    string[] fileDirs = fullPath.Split(new char[] { ':', '\\', '/' });

    // if we failed to split (empty strings?) or the drive letter does not match
    if( baseDirs.Length <= 0 || fileDirs.Length <= 0 || baseDirs[0] != fileDirs[0] )
    {
        // can't create a relative path between separate harddrives/partitions.
        return fullPath;
    }

    // skip all leading directories that match
    for (offset = 1; offset < baseDirs.Length; offset++)
    {
        if (baseDirs[offset] != fileDirs[offset])
            break;
    }

    // back out of the working directory
    for (int i = 0; i < (baseDirs.Length - offset); i++)
    {
        result += "..\\";
    }

    // step into the file path
    for (int i = offset; i < fileDirs.Length-1; i++)
    {
        result += fileDirs[i] + "\\";
    }

    // append the file
    result += fileDirs[fileDirs.Length - 1];

    return result;
}

这段代码可能不是防弹的，但这是我想出的。它更健壮一些。它需要两条路径，并返回相对于路径 A 的路径 B。

示例：

MakeRelativePath("c:\\dev\\foo\\bar", "c:\\dev\\junk\\readme.txt")
//returns: "..\\..\\junk\\readme.txt"

MakeRelativePath("c:\\dev\\foo\\bar", "c:\\dev\\foo\\bar\\docs\\readme.txt")
//returns: "docs\\readme.txt"

Answer 4

感谢这里的其他答案，经过一些实验，我创建了一些非常有用的扩展方法：

public static string GetRelativePathFrom(this FileSystemInfo to, FileSystemInfo from)
{
    return from.GetRelativePathTo(to);
}

public static string GetRelativePathTo(this FileSystemInfo from, FileSystemInfo to)
{
    Func<FileSystemInfo, string> getPath = fsi =>
    {
        var d = fsi as DirectoryInfo;
        return d == null ? fsi.FullName : d.FullName.TrimEnd('\\') + "\\";
    };

    var fromPath = getPath(from);
    var toPath = getPath(to);

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

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

    return relativePath.Replace('/', Path.DirectorySeparatorChar);
}

要点：

• 使用FileInfo 和DirectoryInfo 作为方法参数，这样就不会对正在处理的内容产生歧义。 Uri.MakeRelativeUri 期望目录以斜杠结尾。
• DirectoryInfo.FullName 不会规范化尾部斜杠。它输出构造函数中使用的任何路径。此扩展方法会为您解决这些问题。

Answer 5

还有a way to do this with some restrictions。这是文章中的代码：

public string RelativePath(string absPath, string relTo)
    {
        string[] absDirs = absPath.Split('\\');
        string[] relDirs = relTo.Split('\\');
        // Get the shortest of the two paths 
        int len = absDirs.Length < relDirs.Length ? absDirs.Length : relDirs.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 (absDirs[index] == relDirs[index])
                lastCommonRoot = index;
            else break;
        }
        // If we didn't find a common prefix then throw 
        if (lastCommonRoot == -1)
        {
            throw new ArgumentException("Paths do not have a common base");
        }
        // Build up the relative path 
        StringBuilder relativePath = new StringBuilder();
        // Add on the .. 
        for (index = lastCommonRoot + 1; index < absDirs.Length; index++)
        {
            if (absDirs[index].Length > 0) relativePath.Append("..\\");
        }
        // Add on the folders 
        for (index = lastCommonRoot + 1; index < relDirs.Length - 1; index++)
        {
            relativePath.Append(relDirs[index] + "\\");
        }
        relativePath.Append(relDirs[relDirs.Length - 1]);
        return relativePath.ToString();
    }

执行这段代码时：

string path1 = @"C:\Inetpub\wwwroot\Project1\Master\Dev\SubDir1"; 
string path2 = @"C:\Inetpub\wwwroot\Project1\Master\Dev\SubDir2\SubDirIWant";

System.Console.WriteLine (RelativePath(path1, path2));
System.Console.WriteLine (RelativePath(path2, path1));

打印出来：

..\SubDir2\SubDirIWant
..\..\SubDir1