1. 获取绝对文件路径

System.IO.Path.GetFullPath(string path)

string fileName = "myfile.ext";
string path1 = @"mydir";
string path2 = @"\mydir";
string fullPath;

fullPath = Path.GetFullPath(path1);
fullPath = Path.GetFullPath(fileName);
fullPath = Path.GetFullPath(path2);

2. 获取文件名字(得到指定路径内的文件名，不包括扩展名)

System.IO.Path.GetFileNameWithoutExtension(string path)
string fileName = @"C:\mydir\myfile.ext";
string path = @"C:\mydir\";
string result;
result = Path.GetFileNameWithoutExtension(fileName);
result = Path.GetFileName(path);

3.获得包含 path 目录信息的string 或者为空引用

System.IO.Path.GetDirectoryName(string path)

string fileName = @"C:\mydir\myfile.ext";
string path = @"C:\mydir\";
string rootPath = @"C:\";
string directoryName;
    
directoryName = Path.GetDirectoryName(fileName);
directoryName = Path.GetDirectoryName(path);
directoryName = Path.GetDirectoryName(rootPath);

4.合并两个路径字符串。

System.IO.Path.Combine(String path1, String path2)