Inject custom created object based on claims

Question

I'm using claims based authentication in my Blazor Server app. When the user logs in to my app, I define a claim which contains a specific ID to identify the user within the database.

Now I want to get an object based on its value which I can use within my app.

For example: let's say the value from my claim is 1. Now I need a way to get the data for user 1 from the database and inject the object into my razor components/pages to make all properties accessible at any time within my app. I think this can be achieved with some sort of middleware but I'm not sure about this.

My current approach is to access the HttpContext within the _Host.cshtml file which loads the appropriate data to the page on a page reload but not when changing pages using a NavLink or the NavigationManager.

How can I get the relevant data to load each time the active page is changed?

Answer 1

I tried to adjust @Hans code but by using AuthenticationStateProvider

using System.Security.Claims
using Microsoft.AspNetCore.Components.Authorization

public class ClaimsPrincipalDataService
{
    private readonly AuthenticationStateProvider AuthenticationStateProvider;
    private readonly DbContext DbContext;

    public ClaimsPrincipalDataService(AuthenticationStateProvider AuthenticationStateProvider , DbContext DbContext)
    {
        this.AuthenticationStateProvider  = AuthenticationStateProvider;
        this.DbContext = DbContext;
    }

    private async Task<User> GetUserAsync()
    {
       var authState = await AuthenticationStateProvider.GetAuthenticationStateAsync();
        var user = authState.User;
      if (user.Identity.IsAuthenticated)
        {
            var userId = user.FindFirst(ClaimTypes.NameIdentifier).Value;
           return await DbContext.Users.FindAsync(userId);
        }
        else
        {
            //do something
        }
    }
}

Add scope

services.AddScoped<ClaimsPrincipalDataService>();

Inject the service in your component

@inject ClaimsPrincipalDataService ClaimService

@code {
    private User _user;

    protected override async Task OnInitializedAsync()
    {
        _user = await ClaimService.GetUserAsync();
    }
}