User.Identity.IsAuthenticated always false in .net core custom authentication

You can try this one. I think this can help

var userIdentity = new ClaimsIdentity( claims, AuthenticationTypes.Basic);

In my case the problem was in the startup file. app.UseAuthentication() line was coming after app.UseMvc() line.I reversed the orders and it started to work.

I know this question was asked a long time ago, but it might be useful to another person.

Using app.UseAuthentication(); right before app.UseAuthorization(); inside the Configure method in the Startup.cs class fixed it for me.

ClaimsIdentity.IsAuthenticated returns false when ClaimsIdentity.AuthenticationType is null or empty. To avoid that, stop using the parameterless ClaimsIdentity constructor and use the overload accepting an authenticationType parameter:

var userIdentity = new ClaimsIdentity("Custom");