[HttpPost]
public AttachmentDto CreateAttachment(JObject json)
{
    using (var _client = new DataServiceClient("epData"))
    {
        if (Properties.Settings.Default.Domain != "")
        {
            _client.ClientCredentials.Windows.ClientCredential.UserName = Properties.Settings.Default.Domain + "\" + Properties.Settings.Default.Login;
            _client.ClientCredentials.Windows.ClientCredential.Password = Properties.Settings.Default.Password;
        }
        var userId = json["userId"].ToObject<Guid>();
        _client.SetCurrentUser(userId);


        var filePath = json["filePath"].ToObject<string>();

        var originalFilePath = Convert.FromBase64String(filePath);
        var fileName = json["fileName"].ToObject<string>();
        var categoryId = json["categoryId"].ToObject<Guid>();

        var result = _client.CreateAttachment(fileName, categoryId, data);
        return null;
    }
}