asp.net中计算文件夹的大小

public long GetDirectoryLength(string dirPath)
{
if (!Directory.Exists(dirPath))
return 0;
long len = 0;
DirectoryInfo di = new DirectoryInfo(dirPath);
foreach (FileInfo fi in di.GetFiles())
{
len += fi.Length;
}
DirectoryInfo[] dis = di.GetDirectories();
if (dis.Length > 0)
{
for (int i = 0; i < dis.Length; i++)
{
len += GetDirectoryLength(dis[i].FullName);
}
}
return len;
}