Inject custom created object based on claims-CodePudding

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?

CodePudding user response：

One approach you could take is to use dependency injection to inject the object into your Razor components/pages. You could create a service class that retrieves the object from the database based on the user's ID, and then inject an instance of that service into your components/pages.

For example, you could define a service like this:

public class UserService
{
    private readonly IHttpContextAccessor _httpContextAccessor;
    private readonly MyDbContext _dbContext;

    public UserService(IHttpContextAccessor httpContextAccessor, MyDbContext dbContext)
    {
        _httpContextAccessor = httpContextAccessor;
        _dbContext = dbContext;
    }

    public async Task<User> GetUserAsync()
    {
        var userId = _httpContextAccessor.HttpContext.User.FindFirst(ClaimTypes.NameIdentifier).Value;
        return await _dbContext.Users.FindAsync(userId);
    }
}

Then, you can register this service in your app's Startup class:

services.AddScoped<UserService>();

Finally, you can inject an instance of the service into your component or page and use it to retrieve the user object:

@inject UserService UserService

@code {
    private User _user;

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

This way, the user object will be refreshed each time the component or page is rendered, so any changes to the object in the database will be reflected in the app.

Note that you will need to add the IHttpContextAccessor service to your app's service collection in order for the UserService to be able to access the current user's claims. You can do this by adding the following line to the ConfigureServices method in your Startup class:

services.AddHttpContextAccessor();

CodePudding user response：

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();
    }
}