I am fairly new to coding with asp.net so there might be an obvious answere to my question but I haven't found one yet.
So currently I am developing a site for project management and I want the users to get notified when an event happens, eg. they were added to a new project, a project has been updated etc.
For that I have expanded the IdentityUser Model with a new property List
public class CojectUser : IdentityUser
{
public List<Notification> Notifications { get; set; }
}
public class Notification
{
public int NotificationID { get; set; }
public string Message { get; set; }
public bool Seen { get; set; }
}
When an event happens I add them to the user's notification list and update the user via the userManager.
public class EventBroker<T> : IEventBroker<T>
{
private readonly UserManager<CojectUser> userManager;
public EventBroker(UserManager<CojectUser> userMgr, IUserValidator<CojectUser> userValid)
{
userManager = userMgr;
}
public async Task NotifyAsync(Message<T> message, List<UserRole> recipients)
{
foreach (var user in recipients)
{
var cojectUser = await userManager.FindByNameAsync(user.Name);
if (cojectUser != null)
{
if (cojectUser.Notifications == null)
{
cojectUser.Notifications = new List<Notification>();
}
cojectUser.Notifications.Add(new Notification
{
Message = message.Information,
Seen = false
});
IdentityResult result = await userManager.UpdateAsync(cojectUser);
if (!result.Succeeded)
{
throw new UserUpdateFailException();
}
}
}
}
}
}
I am able to save the custom data to the database, but I am unable to load it again from database.
When I want to display the user's notifications userManager retrieves an user object with null as notification list. Even though the data is stored in database.
public async Task<IActionResult> Index()
{
CojectUser user = await userManager.GetUserAsync(User);
if(user.Notifications == null)
{
user.Notifications = new List<Notification>();
}
return View(user);
}
Data in database:
Can anybody tell me what I am doing wrong?
UserManager don't eager load properties by default.
You should use DatabaseContext directly.
var user = _context.Users.Include(c => c.Notifications).Where(u => u.Id == user.Id).ToList();
The rule is that controllers shouldn't have business logic, instead they should delegate it to the services. But when we do that, we can't handle all possible cases and return appropriate HTTP response.
Let's look at an example. Let's say that we are building some kind of a social network, and we need to create an endpoint for rating (liking or disliking) a post.
First let's take a look at an example where we delegate the logic to the service, this is our controller action:
public IActionResult Rate(long postId, RatingType ratingType)
{
var user = GetCurrentUser();
PostRating newPostRating = _postsService.Rate(postId, ratingType, user);
return Created(newPostRating);
}
Do you see a problem in this? What if there is no post with the given id, how would we return a not found response? What if user has no permissions to rate a post, how would we return a forbidden response?
PostsService.Rate can only return a new PostRating, but what about other cases? Well, we could throw an exception, we would need to create a lot of custom exception, so that we can map them to the appropriate HTTP responses. I don't like to use exceptions for this, I think there is a better way to do handle these cases instead of exceptions. Because I think that cases when post doesn't exist and when user has no permissions aren't exceptional at all, they're just normal cases just like rating a post successfully.
What I propose, is handling that logic in a controller instead. Because in my opinion, that should be a controllers responsibility anyway, to check all of the permissions before commiting an action. So this is how I would do it:
public IActionResult Rate(long postId, RatingType ratingType)
{
var user = GetCurrentUser();
var post = _postsRepository.GetByIdWithRatings(postId);
if (post == null)
return NotFound();
if (!_permissionService.CanRate(user, post))
return Forbidden();
PostRating newPostRating = new PostRating
{
Post = post,
Author = user,
Type = ratingType
};
_postRatingsRepository.Save(newPostRating);
return Created(newPostRating);
}
This is the way it should be done in my opinion but I bet that someone would say that this is too much logic for the controller, or that you shouldn't use a repository in it.
If you don't like using a repository in controller than where instead would you put a method that gets or saves posts? In service? So there would be PostsService.GetByIdWithRatings and PostsService.Save that would do nothing else but just call PostsRepository.GetByIdWithRatings and PostsRepository.Save. This so unnecessary and only causes boilerplate code.
Update:
Maybe someone will say to check the permissions using PostsService and then call PostsService.Rate. This is bad because it involves more unnecessary trips to database. For an example, it would probably be something like this:
public IActionResult Rate(long postId, RatingType ratingType)
{
var user = GetCurrentUser();
if(_postsService.Exists(postId))
return NotFound();
if(!_postsService.CanUserRate(user, postId))
return Forbidden();
PostRating newPostRating = _postsService.Rate(postId, ratingType, user);
return Created(newPostRating);
}
Do I even need to explain any further why this is bad?
There's a number of ways to handle this, but the closest thing to a "best practice" method is probably using a result class. For example, if your service method creates a rating and then returns that rating it created, you instead return an object that encapsulates the rating along with other relevant information, such as success status, error messages, if any etc.
public class RateResult
{
public bool Succeeded { get; internal set; }
public PostRating PostRating { get; internal set; }
public string[] Errors { get; internal set; }
}
Then, your controller code would become something like:
public IActionResult Rate(long postId, RatingType ratingType)
{
var user = GetCurrentUser();
var result = _postsService.Rate(postId, ratingType, user);
if (result.Succeeded)
{
return Created(result.PostRating);
}
else
{
// handle errors
}
}
What I did (just now) is created new class ApiResult
public class ApiResult
{
public int StatusCode { get; private set; } = 200;
public string RouteName { get; private set; }
public object RouteValues { get; private set; }
public object Content { get; private set; }
public void Ok(object content = null)
{
this.StatusCode = 200;
this.Content = content;
}
public void Created(string routeName, object routeValues, object content)
{
this.StatusCode = 201;
this.RouteName = routeName;
this.RouteValues = routeValues;
this.Content = content;
}
public void BadRequest(object content = null)
{
this.StatusCode = 400;
this.Content = content;
}
public void NotFound(object content = null)
{
this.StatusCode = 404;
this.Content = content;
}
public void InternalServerError(object content = null)
{
this.StatusCode = 500;
this.Content = content;
}
}
And a controller base class with a single method TranslateApiResult
public abstract class CommonControllerBase : ControllerBase
{
protected IActionResult TranslateApiResult(ApiResult result)
{
if (result.StatusCode == 201)
{
return CreatedAtAction(result.RouteName, result.RouteValues, result.Content);
}
else
{
return StatusCode(result.StatusCode, result.Content);
}
}
}
And now in controller I do:
[ApiController]
[Route("[controller]/[action]")]
public class MyController : CommonControllerBase
{
private readonly IMyApiServcie _service;
public MyController (
IMyApiServcie service)
{
_service = service;
}
[HttpGet]
public async Task<IActionResult> GetData()
{
return TranslateApiResult(await _service.GetData());
}
}
In your services you inject repositories and other dependencies:
public class MyApiServcie : IMyApiServcie
{
public async Task<ApiResult> GetData()
{
var result = new ApiResult();
// do something here
result.Ok("success");
return result;
}
}
Now, the reason for Api prefix before the Service is that this service is not meant to be the final service containing all logic.
At this point I would split the business logic into different domains so the services (or facades) would end up without Api prefix in them just to differentiate between i.e. CarService. Preferably these services will not know of anything related to API responses, statuses etc. It's up to you how implement it, though.
When I try to run my Xamarin Forms application on an actual iPhone, it fails with a System.MissingMethodException: "Constructor on type 'System.ComponentModel.ReferenceConverter' not found."
It works fine on the iOS Simulators as well as on Android hardware and virtual devices.
I've been able to narrow it down to the following scenario: serializing an object with an interface referenced member:
public class Widget {
public ISprocket Sprocket { get; set; };
}
public interface ISprocket {
int SprocketId { get; set; }
}
Executing the lines:
var w = new Widget { Sprocket = new Sprocket { SprocketId = 1 } };
string result = JsonConvert.SerializeObject(w);
works everywhere (seemingly) except on my iPhone 8+, where it throws a System.MissingMethodException
I'm using the most current versions of XF (2.5.0.122203) and JSON.NET (10.0.3).
To recreate this problem, create a new Xamarin Forms solution with an iOS client called "TestBed". Add Newtonsoft.Json via nuget, then create a page
"TestBedPage" with the following content:
using System;
using Newtonsoft.Json;
using Xamarin.Forms;
namespace TestBed
{
public class TestBedPage : ContentPage
{
public TestBedPage()
{
try
{
var m = new Widget { Sprocket = new Sprocket { SprocketId = 1 } };
var st = JsonConvert.SerializeObject(m);
Content = new Label { Text = st };
} catch (Exception ex) {
Content = new Label { Text = ex.ToString() };
}
}
}
public class Widget
{
public string Title { get; set; } = string.Empty;
public ISprocket Sprocket { get; set; }
}
public interface ISprocket
{
int SprocketId { get; set; }
}
public class Sprocket : ISprocket
{
public int SprocketId { get; set; }
}
}
Deploy it to an iPhone and run. You should get a screenful of MissingMethodException stack trace.
Does anyone have any idea what's going on here?
The issue is that something is trying to instantiate via Activator class an instance of System.ComponentModel.ReferenceConverter via its System.Type ctor but since it isn't referenced directly in you application it gets removed by the managed linker.
You need to provide a custom linker configuration file ,add it to your Xamarin.iOS project.
Refer to here
I am using ASP.NET EntityFramework MVC (All Latest) with Visual Studio 2013.
I am attempting to come up with a unifying means of standardizing the abstraction between my object and data layer.
I know that many people like to use the IRepository pattern with MVC. My biggest issue with this is that it forces you to create and maintain a second object type (The Repository) for each of the objects that you want to maintain. My solution has been to combing the IRepository method with a Static Factory pattern to make a Static Repository, for instance:
public class SiteDatabase : DbContext
{
// Singleton
private static SiteDatabase _Instance;
public static SiteDatabase Instance
{
get
{
if (_Instance == null)
{
_Instance = new SiteDatabase();
}
return _Instance;
}
}
public DbSet<User> Users { get; set; }
}
public class User : IUser
{
public static User Create(string UserName)
{
User item = new User();
item.UserName = UserName;
SiteDatabase.Instance.Users.Add(item);
return item;
}
public static User Find(string UserName)
{
return SiteDatabase.Instance.Users.SingleOrDefault(x => x.UserName == UserName);
}
public static User[] All()
{
return SiteDatabase.Instance.Users.ToArray();
}
public string Id { get; set; }
public string UserName { get; set; }
protected User()
{
Id = Guid.NewGuid().ToString();
}
public void Delete()
{
SiteDatabase.Instance.Users.Remove(this);
}
}
public class Page
{
public static Page Create(string PageName)
{
...
}
public static Page Find(string PageName)
{
...
}
public static Page[] All()
{
...
}
...
public void Delete()
{
...
}
}
My question is: will this pattern cause me to miss out on any built-in functionality that the normal repository pattern would allow me to capture?
The non-static methods could be handled with an interface, but what about the static methods? Is there any way to have a base class that ensures that static methods will exist in derived classes?
I trying to write a kind of pseudo singleton implementation. I want it to work similar to how HttpContext does work, where I can get an instance to the context doing something as simple as:
var ctx = HttpContext.Current;
So my implementation goes something like this:
public class AppUser
{
public string Username { get; set; }
public string[] Roles { get; set; }
public AppUser()
{
var appuser = HttpContext.Session["AppUser"] as AppUser;
if(appuser == null)
throw new Exception("User session has expired");
Username = appuser.Username;
Roles = appuser.Roles;
}
}
public class WebAppContext
{
const string ContextKey = "WebAppContext";
WebAppContext() { } //empty constructor
public static WebAppContext Current
{
get
{
var ctx = HttpContext.Current.Items[ContextKey] as WebAppContext;
if(ctx == null)
{
try
{
ctx = new WebAppContext() { User = new AppUser() };
}
catch
{
//Redirect for login
}
HttpContext.Current.Items.Add(ContextKey, ctx);
}
return ctx;
}
}
public AppUser User { get; set; }
}
And I try to consume this object as follows:
var appuser = WebAppContext.Current.User;
Now does the above line guarantee I get the user associated with the correct request context; not some other user which is associated with another concurrent http request being processed?
Apart from the fact that I can't understand why would you need to barely copy the user information from the Session container to the Items container, the answer to your question should be - yes, if the Session data is correct then the same data will be available from your static property.
I wrote a blog entry on that once
http://netpl.blogspot.com/2010/12/container-based-pseudosingletons-in.html