得到目录大小

public static long DirSize(DirectoryInfo d)     {            long Size = 0;            // Add file sizes.         FileInfo[] fis = d.GetFiles();         foreach (FileInfo fi in fis)         {                  Size += fi.Length;            }         // Add subdirectory sizes.         DirectoryInfo[] dis = d.GetDirectories();         foreach (DirectoryInfo di in dis)         {             Size += DirSize(di);           }         return(Size);      }