JWT Authentication – UserManager.GetUserAsync returns null

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UserManager.GetUserAsync internally uses UserManager.GetUserId to retrieve the user id of the user which is then used to query the object from the user store (i.e. your database).

GetUserId basically looks like this:

public string GetUserId(ClaimsPrincipal principal)
{
    return principal.FindFirstValue(Options.ClaimsIdentity.UserIdClaimType);
}

So this returns the claim value of Options.ClaimsIdentity.UserIdClaimType. Options is the IdentityOptions object that you configure Identity with. By default the value of UserIdClaimType is ClaimTypes.NameIdentifier, i.e. "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/nameidentifier".

So when you try to use UserManager.GetUserAsync(HttpContext.User), where that user principal has a UserID claim, the user manager is simply looking for a different claim.

You can fix this by either switchting to the ClaimTypes.NameIdentifier:

new ClaimsIdentity(new[]
{
    new Claim(ClaimTypes.Name, user.UserName),
    new Claim(ClaimTypes.NameIdentifier, user.Id.ToString()),
})

Or you configure Identity properly so it will use your UserID claim type:

// in Startup.ConfigureServices
services.AddIdentity(options => {
    options.ClaimsIdentity.UserIdClaimType = "UserID";
});

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