Asp .Net Core 5 Identity - How to fetch a user? - jwt

Question

In the new SPA (react and angular) web templates for .Net core 5. I'd like to fetch the current logged in User. However, when I try to get a user in the controller the User doesn't have anything populated.
Does anyone know how to achieve this with the new Identity Classes?
I've made a repo of the vanilla reactJS template, the only thing I changed is the line highlighted in my screenshot below to show there's no user set.
I've done a bit of googling and these pages are all I could find on the topic, unfortunately, they don't give enough detail for me to be able to implement anything practical.
https://learn.microsoft.com/en-us/aspnet/core/security/authentication/identity-api-authorization?view=aspnetcore-5.0
https://learn.microsoft.com/en-us/aspnet/core/security/authorization/claims?view=aspnetcore-5.0

Answer 1

Backend:
ClaimsPrincipal currentUser = this.User;
var currentUserName = currentUser.FindFirst(ClaimTypes.NameIdentifier).Value;
ApplicationUser user = await _userManager.FindByNameAsync(currentUserName);
On the frontend if you need yo access it
//with UserManager
UserManager<ApplicationUser> UserManager
#{
var user = await UserManager.GetUserAsync(User);
}
// with SignInManager
SignInManager<ApplicationUser> SignInManager
#if (SignInManager.IsSignedIn(User))

Answer 2

To answer my own question.
In order to populate the User detail in the HttpContext you have 1 of 2 routes. Either change
services.AddDefaultIdentity<IdentityUser>();
to
services.AddIdentity<IdentityUser, IdentityRole>();
or you can continue to use the Core Identity
services.AddIdentityCore<IdentityUser>();
but then you also need to implement your own Microsoft.AspNetCore.Identity.ISecurityStampValidator and add it as transient services.AddTransient<ISecurityStampValidator, MyValidator>();
Your MyValidator implementation will be responsible for validating the cookie. You can see the default implementation here on github
Edit: Under the hood services.AddDefaultIdentity<IdentityUser>(); uses services.AddIdentityCore<IdentityUser>();. I feel like its importatnt to know this.