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); 
     }