获得文件的HASH值

    public string GetFileHash(string filepath)
    {
        FileStream filestream = new FileStream(filepath, FileMode.Open, FileAccess.Read, FileShare.Read);
        System.Security.Cryptography.MD5CryptoServiceProvider md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
        byte[] byt = md5.ComputeHash(filestream);
        string hashcode = BitConverter.ToString(byt);
        hashcode = hashcode.Replace("-", "");
        return hashcode;
    }

可以唯一标示文件 挺有用。