char a = System.IO.Path.VolumeSeparatorChar;//  :
char b = System.IO.Path.DirectorySeparatorChar;//  \

string filePath =@”c:\folder\file.txt”;

Path.ChangeExtension(filePath, ".html");// c:\folder\file.htm
Path.Combine("c:\folder", "file.txt");// c:\folder\file.txt
Path.IsPathRooted(filePath);    // true
Path.GetPathRoot(filePath);     // C:\
Path.GetDirectoryName(filePath);// c:\folder
Path.GetFileName(filePath);     // file.txt
Path.GetFileNameWithoutExtension(filePath);// file
Path.HasExtension(filePath);    // true
Path.GetExtension(filePath);    // .txt
Path.GetFullPath(filePath);     // c:\folder\file.txt