public async Task <ExternalRegisterUserDto> GetExternalData(IExternalDataDto externalData) { if (!(externalData is FacebookExternalDataDto facebookExternalData)) { throw new ArgumentNullException(nameof(facebookExternalData)); } var facebookUserDto = await _facebookClient.GetFacebookUserData(facebookExternalData.AccessToken); var result = _mapper.Map <ExternalRegisterUserDto>(facebookUserDto); return(result); }