How to check/redirect in every method of any controller in ASP NET Core 3.1?

I’m looking for a way to do this in every Method of every Controller, even for those that doesn’t return an IActionResult (I’ll talking about this forward):

1. Get User.Claim to get the user info logged into the site.
2. Check if the user is blocked in the database (I’ve my own repositories working already)
3. Redirect a user to a Page that shows “you are blocked” like the workflow of Exceptions does.

Considerations and tries that I already made:

• Can’t get this from a Claim in order to work it with ViewStart because I need the block works in the same moment the database were updated. The Claim should the user sign out and sign in.
• Can’t do this trough a controller that returns a boolean with Json in
  every page because the user could stop the redirect
• I’ve several methods that returns partialviews, objects, lists, anything but IActionResult. I don’t care if that doesn’t work for two reasons:
  • It should be triggered by the main view that calls those through ajax.
  • The user is blocked anyway so I don’t care if it see the page broken.
• My security workflow is like this:

  [HttpPost]
  [Authorize(Policy = "Users")]
  [Authorize(AuthenticationSchemes = "MyAppScheme")]
  
  public IActionResult GetRep() {
       //Do things
  }

Right now I’m trying do a middleware but I’m new in NET Core at so deep level, so can’t compile neither. Also working trying to call my userRepository from the ViewStart

Answers:

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Method 1

The best way is using a middleware. Here you have an example:

internal class UserMiddleware
{
    private readonly RequestDelegate next;
    private readonly IUserRepository userRepository;

    public UserMiddleware(RequestDelegate next, IUserRepository userRepository)
    {
        this.next = next ?? throw new ArgumentNullException(nameof(next));
        this.userRepository = userRepository ?? throw new ArgumentNullException(nameof(userRepository));
    }

    public async Task Invoke(HttpContext httpContext)
    {
        Claim clientId = httpContext.User.FindFirst(ClaimTypes.NameIdentifier);
        bool isBlocked = await this.userRepository.CheckUser(clientId);

        if (isBlocked)
        {
            await httpContext.Response.WriteAsync("You are blocked.");
            return;
        }

        await this.next(httpContext);
    }
}

Then in your startup method you should call it before mapping your controllers:

public static void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // Other stuff...

    app.UseMiddleware<UserMiddleware>();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}

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