FindRelativePathInAncestors

FindRelativePathInAncestors.cs

/// <summary>
/// Search for relativePath with respect to (w.r.t.) the current directory and if it doesn't exist,
/// search w.r.t. the current parent directory, then the grandparent and so on until the path is found
/// or the root it hit. Works for files or directories.
/// </summary>        
/// <returns></returns>
public static string FindRelativePathInAncestors(string relativePath, string startDirectory)
{
    relativePath = relativePath.TrimStart(Path.DirectorySeparatorChar);
    int level = 0;
    var root = Path.GetPathRoot(startDirectory);
    while (true)
    {                
        var prefix = "." + string.Join("/", Enumerable.Repeat("..", level));
        var absolutePrefix = Path.GetFullPath(Path.Combine(startDirectory, prefix));
        var testPath = Path.Combine(absolutePrefix, relativePath);
        if (File.Exists(testPath) || Directory.Exists(testPath))
            return testPath;
        if (absolutePrefix == root)
            return null;                             
        level++;
    }            
}