从路径字符串或FileInfo获取驱动器号

using System;
using System.IO;

class Program
{
    static void Main(string[] args)
    {
        string path = @"C:\Users\Public\Documents\MyFile.txt";
        string driveLetter = GetDriveLetterFromPath(path);
        Console.WriteLine($"驱动器号：{driveLetter}");

        FileInfo fileInfo = new FileInfo(path);
        driveLetter = GetDriveLetterFromFileInfo(fileInfo);
        Console.WriteLine($"驱动器号：{driveLetter}");
    }

    static string GetDriveLetterFromPath(string path)
    {
        string driveLetter = string.Empty;
        if (Path.IsPathRooted(path))
        {
            driveLetter = Path.GetPathRoot(path);
        }
        return driveLetter;
    }

    static string GetDriveLetterFromFileInfo(FileInfo fileInfo)
    {
        string driveLetter = string.Empty;
        if (fileInfo.FullName.Length >= 2)
        {
            driveLetter = fileInfo.FullName.Substring(0, 2);
        }
        return driveLetter;
    }
}