计算相对于一些路径根 - Path.Combine的逆 [英] Calculating the path relative to some root- the inverse of Path.Combine

问题描述

有没有一种可靠的方法来计算Path.Combine（）？

Is there a reliable way to calculate the inverse of Path.Combine()?

Path.Combine（C：\文件夹，子目录\ something.txt）可能会返回类似C：\文件夹\子目录\ something.text。我要的是相反的，一个函数，其中Path.GetRelativeUrl（C：\文件夹，C：\文件夹\子目录\ something.text）。将返回类似子目录\ something.txt

Path.Combine("c:\folder", "subdirectory\something.txt") might return something like "c:\folder\subdirectory\something.text". What I want is the inverse, a function where Path.GetRelativeUrl("c:\folder", "c:\folder\subdirectory\something.text") would return something like ""subdirectory\something.txt".

的一个解决方案是做字符串比较和修整根，但是这不会工作时相同的路径是前pressed以不同的方式（使用..或〜1在路径前pression）。

One solution is to do string comparisons and trim the roots, but this would not work when the same path is expressed in different ways (use of ".." or "~1" in path expression).

推荐答案

好吧，所以在我来说，我没有一些更严厉的边缘情况（FULLPATH和relativePath混合网络地图位置，超长文件名）。我最终什么做什么是创建以下

Alright so in my case I don't have some of the tougher edge cases (fullPath and relativePath mixing network map locations, super long filenames). What I ended up doing was creating the class below

public class PathUtil
{
    static public string NormalizeFilepath(string filepath)
    {
        string result = System.IO.Path.GetFullPath(filepath).ToLowerInvariant();

        result = result.TrimEnd(new [] { '\\' });

        return result;
    }

    public static string GetRelativePath(string rootPath, string fullPath)
    {
        rootPath = NormalizeFilepath(rootPath);
        fullPath = NormalizeFilepath(fullPath);

        if (!fullPath.StartsWith(rootPath))
            throw new Exception("Could not find rootPath in fullPath when calculating relative path.");

        return "." + fullPath.Substring(rootPath.Length);
    }
}

看来工作pretty的好。至少，它通过了这些测试NUnit的：

It seems to work pretty well. At least, it passes these NUnit tests:

[TestFixture]
public class PathUtilTest
{
    [Test]
    public void TestDifferencesInCapitolizationDontMatter()
    {
        string format1 = PathUtil.NormalizeFilepath("c:\\windows\\system32");
        string format2 = PathUtil.NormalizeFilepath("c:\\WindowS\\System32");

        Assert.AreEqual(format1, format2);
    }

    [Test]
    public void TestDifferencesDueToBackstepsDontMatter()
    {
        string format1 = PathUtil.NormalizeFilepath("c:\\windows\\system32");
        string format2 = PathUtil.NormalizeFilepath("c:\\Program Files\\..\\Windows\\System32");

        Assert.AreEqual(format1, format2);
    }

    [Test]
    public void TestDifferencesInFinalSlashDontMatter()
    {
        string format1 = PathUtil.NormalizeFilepath("c:\\windows\\system32");
        string format2 = PathUtil.NormalizeFilepath("c:\\windows\\system32\\");

        Console.WriteLine(format1);
        Console.WriteLine(format2);

        Assert.AreEqual(format1, format2);
    }

    [Test]
    public void TestCanCalculateRelativePath()
    {
        string rootPath = "c:\\windows";
        string fullPath = "c:\\windows\\system32\\wininet.dll";
        string expectedResult = ".\\system32\\wininet.dll";

        string result = PathUtil.GetRelativePath(rootPath, fullPath);

        Assert.AreEqual(expectedResult, result);
    }

    [Test]
    public void TestThrowsExceptionIfRootDoesntMatchFullPath()
    {
        string rootPath = "c:\\windows";
        string fullPath = "c:\\program files\\Internet Explorer\\iexplore.exe";

        try
        {
            PathUtil.GetRelativePath(rootPath, fullPath);
        }
        catch (Exception)
        {
            return;
        }

        Assert.Fail("Exception expected");
    }
}

测试用例依靠现有的..这些文件在大多数Windows安装，但您的情况可能有所不同某些共同文件。

The test cases rely on certain files existing.. these files are common on most Windows installs but your mileage may vary.

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