Given a file path which is missing the file extension, search the directory for a matching file and return its full path, including extension

MatchingFileWithUnknownExtension.cs

/// <summary>
/// Given a path to a file which is missing the file extension, search the directory
/// for a matching file and return its full path (with extension)
/// </summary>
/// <param name="localPath">Path to a file without file extension</param>
/// <returns>The path with the file extension</returns>
private static string MatchingFileWithUnknownExtension(string localPath)
{
    string directory = Path.GetDirectoryName(localPath);
    string fileNameWithoutExtension = Path.GetFileNameWithoutExtension(localPath);
    string matchingFile = Directory.EnumerateFiles(directory)
        .Where(f => Path.GetFileNameWithoutExtension(f) == fileNameWithoutExtension)
        .FirstOrDefault();
    return matchingFile;
}