/// <summary>
/// 取文件MD5值
/// </summary>
/// <param name="stream"></param>
/// <returns></returns>
/// <exception cref="ArgumentNullException"></exception>
public static string FileMD5(Stream stream)
{
if (!stream.TrySeek()) return string.Empty;
byte[] bs = MD5.Create().ComputeHash(stream);
stream.TrySeek();
return BitConverter.ToString(bs).Replace("-", "");
}
/// <summary>
/// 通过文件头取扩展名编号
/// </summary>
/// <param name="stream"></param>
/// <returns></returns>
public static string GetFileCode(Stream stream)
{
if (!stream.TrySeek()) return string.Empty;
var r = new BinaryReader(stream);
byte buffer = r.ReadByte();
string bx = buffer.ToString("D3");
buffer = r.ReadByte();
bx += buffer.ToString("D3");
stream.TrySeek();
return bx;
}