Get Current User in a Blazor component

Question

I'm starting a new site with Blazor and Windows Authentication and need to identify the current user viewing the page/component.

For a Razor Page, the current user name can be accessed with Context.User.Identity.Name, but that doesn't seem to work in a Blazor component. I've tried injecting HttpContext into the component but the Context is null at runtime.

As a bonus, I will eventually want to incorporate this into Startup.cs so I only need to get the username once and can leverage a corporate user class (with EF Core) for my applications. Answers tailored to that use case would also be appreciated.

Answer 1

There are three possibilities for getting the user in a component (a page is a component):

1. Inject IHttpContextAccessor and from it access HttpContext and then User; need to register IHttpContextAccessor in Startup.ConfigureServices, normally using AddHttpContextAccessor. Edit: according to the Microsoft docs you must not do this for security reasons.
2. Inject an AuthenticationStateProvider property, call GetAuthenticationStateAsync and get a User from it
3. Wrap your component in a <CascadingAuthenticationState> component, declare a Task<AuthenticationState> property and call it to get the User (similar to #2)

See more here: https://learn.microsoft.com/en-us/aspnet/core/security/blazor.

Answer 2

For me the solution mentioned in the first answer 2. option worked perfect: I am using Blazor server side on .Net Core 5.0 . I injected

@inject AuthenticationStateProvider GetAuthenticationStateAsync

in my Blazor page and added the following in the code section:

protected async override Task OnInitializedAsync()
    {
        var authstate = await GetAuthenticationStateAsync.GetAuthenticationStateAsync();
        var user = authstate.User;
        var name = user.Identity.Name;
    }

In my startup.cs, I have the following lines:

services.AddScoped<ApiAuthenticationStateProvider>();
services.AddScoped<AuthenticationStateProvider>(p =>
                p.GetRequiredService<ApiAuthenticationStateProvider>());

Answer 3

For blazor wasm in net 5.0 and above. Here is how I did,

1. Wrap your <App> component inside <CascadingAuthenticationState> as shown below,

<CascadingAuthenticationState>
    <Router AppAssembly="@typeof(Program).Assembly">
        <Found Context="routeData">
            ...
        </Found>
        <NotFound>
            ...
        </NotFound>
    </Router>
</CascadingAuthenticationState>

2. Then add Task<AuthenticationState> CascadingParameter inside any component as shown below,

public class AppRootBase : ComponentBase
{
    [CascadingParameter] private Task<AuthenticationState> authenticationStateTask { get; set; }
}

3. Now you can access logged in user Identity and Claims inside component as shown below,

protected override async Task OnInitializedAsync()
{
    var authState = await authenticationStateTask;
    var user = authState.User;

    if (user.Identity.IsAuthenticated)
    {
        Console.WriteLine($"{user.Identity.Name} is authenticated.");
    }
}

Here is the reference from Microsoft docs.

Answer 4

I've now been able to get it to work with a general class, as well as a component.

To get access to the HttpContext User; in ConfigureServices, in Startup.cs add

services.AddHttpContextAccessor();

I have a CorporateUserService class for my CorporateUser class. The service class gets a DbContext through constructor injection.

I then created a new CurrentCorporateUserService that inherits from the CorporateUserService. It accepts a DbContext and an IHttpContextAccessor through constructor injection

public class CurrentCorporateUserService : CorporateUserService
{
    private readonly IHttpContextAccessor _httpContextAccessor;

    public CurrentCorporateUserService(IHttpContextAccessor httpContextAccessor,
        MyDbContext context) : base(context)
    {
        _httpContextAccessor = httpContextAccessor;
    }
    ...

The base service class has a method GetUserByUsername(string username). The Current service class adds an additional method

public CorporateUser GetCurrentUser()
{
    return base.GetUserByUsername(_httpContextAccessor.HttpContext.User.Identity.Name.Substring(8));
}

The Current service class is registered in Startup.cs

services.AddScoped<CurrentCorporateUserService>();

Once that is done, I can use the CurrentCorporateUserService in a component with directive injection.

[Inject]
private CurrentCorporateUserService CurrentCorporateUserService { get; set; } = 
default!;

or in any class, with constructor injection.

public MyDbContext(DbContextOptions<MyDbContext> options,
    CurrentCorporateUserService CurrentCorporateUserService)
    : base(options) 
{
    _currentUser = CurrentCorporateUserService.GetCurrentUser();
}

Making it a project wide service means all my developers do not have to concern themselves with how to get the Current User, they just need to inject the service into their class.

For example, using it in MyDbContext makes the current user available to every save event. In the code below, any class that inherits the BaseReport class will automatically have the report metadata updated when the record is saved.

public override Int32 SaveChanges()
{         
    var entries = ChangeTracker.Entries().Where(e => e.Entity is BaseReport
    && (e.State == EntityState.Added || e.State == EntityState.Modified));

    foreach (var entityEntry in entries)
    {
        ((BaseReport)entityEntry.Entity).ModifiedDate = DateTime.Now;
        ((BaseReport)entityEntry.Entity).ModifiedByUser = _currentUser.Username;
    }

    return base.SaveChanges();
}

Answer 5

I've had a similar requirement and have been using:

var authstate = await AuthenticationStateProvider.GetAuthenticationStateAsync();
var user = authstate.User;
var name = user.Identity.Name;

I already had an AuthenticationStateProvider in my startup.cs and added it to the constructor of my custom class.

Answer 6

If you create a new project and choose Blazor with Windows Authentication you get a file called Shared\LoginDisplay.razor with the following content:

<AuthorizeView>
    Hello, @context.User.Identity.Name!
</AuthorizeView>

Using the <AuthorizeView> we can access @context.User.Identity.Name without any modifications on any page.

Answer 7

In your App.razor, make sure the element encapsulated inside a CascadingAuthenticationState element. This is what is generated by default if you create your Blazor project with authentication support.

<CascadingAuthenticationState>
    <Router AppAssembly="@typeof(Program).Assembly" PreferExactMatches="@true">
        <Found Context="routeData">
            <AuthorizeRouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
        </Found>
        <NotFound>
            <LayoutView Layout="@typeof(MainLayout)">
                <p>Sorry, there's nothing at this address.</p>
            </LayoutView>
        </NotFound>
    </Router>
</CascadingAuthenticationState>

In your component you can use the AuthenticationStateProvider to access the current user like in the following sample:

@page "/"

@layout MainLayout

@inject AuthenticationStateProvider AuthenticationStateProvider
@inject SignInManager<IdentityUser> SignInManager

@code
{
    override protected async Task OnInitializedAsync()
    {
        var authenticationState = await AuthenticationStateProvider.GetAuthenticationStateAsync();

        if (SignInManager.IsSignedIn(authenticationState.User))
        {
            //Do something...
        }
    }
}

Answer 8

The below solution works only if you are running under IIS or IIS Express on Windows. If running under kestrel using 'dotnet run', please follow steps here, https://learn.microsoft.com/en-us/aspnet/core/security/authentication/windowsauth?view=aspnetcore-3.0&tabs=visual-studio#kestrel

[startup.cs]

public void ConfigureServices(IServiceCollection services)
{
    services.AddHttpContextAccessor();
}

[index.razor]

@page "/"
@using Microsoft.AspNetCore.Http
@inject IHttpContextAccessor httpContextAccessor

<h1>@UserName</h1>

@code {
    public string UserName;

    protected override async Task OnInitializedAsync()
    {
        UserName = httpContextAccessor.HttpContext.User.Identity.Name;
    }
}

Answer 9

I also had this problem. The best solution I found was to inject both UserManager and AuthenticationStateProvider and then I made these extension functions:

        public static async Task<CustomIdentityUser> GetUserFromClaimAsync(this 
        ClaimsPrincipal claimsPrincipal,
            UserManager<CustomIdentityUser> userManager)
        {
            var id = userManager.GetUserId(claimsPrincipal);
            return await userManager.FindByIdAsync(id);
        }

        public static async Task<CustomIdentityUser> GetCurrentUserAsync(this AuthenticationStateProvider provider, UserManager<CustomIdentityUser> UM)
        {
            return await (await provider.GetAuthenticationStateAsync()).User.GetUserFromClaimAsync(UM);
        }

        public static async Task<string> GetCurrentUserIdAsync(this AuthenticationStateProvider provider, UserManager<CustomIdentityUser> UM)
        {
            return UM.GetUserId((await provider.GetAuthenticationStateAsync()).User);
        }

Answer 10

This was a painful journey for me chasing a moving target. In my case I only needed the user name for my Blazor component used in a Razor page. My solution required the following:

In the Index.cshtml.cs I added two properties and constructor

    public IHttpContextAccessor HttpContextAccessor { get; set; }
    public string UserName { get; set; }

    public TestModel(IHttpContextAccessor httpContextAccessor)
    {
        HttpContextAccessor = httpContextAccessor;
        if (HttpContextAccessor != null) UserName = HttpContextAccessor.HttpContext.User.Identity.Name;
    }

Then in the Index.cshtml where I add the component I called it as follows:

<component type="typeof(MyApp.Components.FileMain)" param-UserName="Model.UserName" render-mode="ServerPrerendered" />

In my component I use a code behind file (FileMain.razor.cs using public class FileMainBase : ComponentBase) have the code:

    [Parameter]
    public string UserName { get; set; } = default!;

and then as a proof of concept I added to the FileMain.razor page

    <div class="form-group-sm">
    <label class="control-label">User: </label>
    @if (UserName != null)
    {
        <span>@UserName</span>
    }
</div>

Answer 11

You should add needed claims to the User after login.

For example I show the FullName on top of site (AuthLinks component) instead of email.

[HttpPost]
    public async Task<IActionResult> Login(LoginVM model)
    {
        var user = await _userManager.FindByNameAsync(model.Email);
        if (user == null || !await _userManager.CheckPasswordAsync(user, model.Password))
            return Unauthorized("Email or password is wrong.");
        var signingCredentials = GetSigningCredentials();
        var claims = GetClaims(user);
        var tokenOptions = GenerateTokenOptions(signingCredentials, claims);
        var token = new JwtSecurityTokenHandler().WriteToken(tokenOptions);
        return Ok(new LoginDto { Token = token, FullName = user.FirstName + " " + user.LastName });
    }

@code {
    private LoginVM loginVM = new();

    [Inject]
    public AuthenticationStateProvider _authStateProvider { get; set; }

    private async Task SubmitForm()
    {
        var response = await _http.PostAsJsonAsync("api/accounts/login", loginVM);
        var content = await response.Content.ReadAsStringAsync();
        var loginDto = JsonSerializer.Deserialize<LoginDto>(content);
        await _localStorage.SetItemAsync("authToken", loginDto.Token);
        _http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", loginDto.Token);
        (_authStateProvider as AuthStateProvider).NotifyLogin(loginDto.FullName);
        _navigationManager.NavigateTo("/");
    }
}

public void NotifyLogin(string fullName)
    {
        var authenticatedUser = new ClaimsPrincipal(new ClaimsIdentity(new[] { new Claim("FullName", fullName) }, "jwtAuthType"));
        var authState = Task.FromResult(new AuthenticationState(authenticatedUser));
        NotifyAuthenticationStateChanged(authState);
    }

<AuthorizeView>
    <Authorized>
        @context.User.FindFirst("FullName")?.Value
        <button class="btn btn-outline-danger mx-4" @onclick="LogOut">LogOut</button>
    </Authorized>
    <NotAuthorized>
        <a href="account/login" class="btn btn-outline-success mx-2">Login</a>
        <a href="account/register" class="btn btn-outline-primary mx-2" style="width:123.44px">Register</a>
    </NotAuthorized>
</AuthorizeView>

GitHub project link: https://github.com/mammadkoma/Attendance

Answer 12

This worked for me:

Replace:

@context.User.Identity.Name

With:

@context.User.Claims.Where(x => x.Type=="name").Select(x => x.Value).FirstOrDefault()

Answer 13

UPDATE - This answer does not work. Rather than deleting it, I've let it here as information. Please consider the other answers for the question instead.

1. In ConfigureServices, in Startup.cs, add services.AddHttpContextAccessor();
2. In your component class [Note: I use code-behind with null types enabled]

        [Inject]
        private IHttpContextAccessor HttpContextAccessor { get; set; } = default!;

        private string username = default!;

3. In your component code (code behind), in protected override void OnInitialized()

        username = HttpContextAccessor.HttpContext.User.Identity.Name;

username can now be used throughout the component just like any other variable.

However, see my other answer in this question to add get the current user name from a service usable in any class.

Answer 14

This is what works for me on a single page

Add to Startup.cs

services.AddHttpContextAccessor();

On the Razor Component page

@using Microsoft.AspNetCore.Http
@inject IHttpContextAccessor httpContextAccessor

<div>@GetCurrentUser()</div>

@code{
    protected string GetCurrentUser()
    {
        return httpContextAccessor.HttpContext.User.Identity.Name;
    }
}