marechai/Marechai/Areas/Identity/Pages/Account/Manage/DownloadPersonalData.cshtml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text.Json;
using System.Threading.Tasks;
using Marechai.Database.Models;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.Extensions.Logging;

namespace Marechai.Areas.Identity.Pages.Account.Manage
{
    public class DownloadPersonalDataModel : PageModel
    {
        readonly ILogger<DownloadPersonalDataModel> _logger;
        readonly UserManager<ApplicationUser>       _userManager;

        public DownloadPersonalDataModel(UserManager<ApplicationUser> userManager,
                                         ILogger<DownloadPersonalDataModel> logger)
        {
            _userManager = userManager;
            _logger      = logger;
        }

        public async Task<IActionResult> OnPostAsync()
        {
            ApplicationUser user = await _userManager.GetUserAsync(User);

            if(user == null)
            {
                return NotFound($"Unable to load user with ID '{_userManager.GetUserId(User)}'.");
            }

            _logger.LogInformation("User with ID '{UserId}' asked for their personal data.",
                                   _userManager.GetUserId(User));

            // Only include personal data for download
            Dictionary<string, string> personalData = new Dictionary<string, string>();

            IEnumerable<PropertyInfo> personalDataProps = typeof(ApplicationUser).
                                                          GetProperties().
                                                          Where(prop =>
                                                                    Attribute.IsDefined(prop,
                                                                                        typeof(PersonalDataAttribute)));

            foreach(PropertyInfo p in personalDataProps)
            {
                personalData.Add(p.Name, p.GetValue(user)?.ToString() ?? "null");
            }

            IList<UserLoginInfo> logins = await _userManager.GetLoginsAsync(user);

            foreach(UserLoginInfo l in logins)
            {
                personalData.Add($"{l.LoginProvider} external login provider key", l.ProviderKey);
            }

            Response.Headers.Add("Content-Disposition", "attachment; filename=PersonalData.json");

            return new FileContentResult(JsonSerializer.SerializeToUtf8Bytes(personalData), "application/json");
        }
    }
}