Extending the UserManager

In my .NET Core 2.0 MVC project I added additional values to extend the ApplicationUser

public class ApplicationUser : IdentityUser
    {
        public string Name { get; set; }
        public DateTime DateCreated { get; set; }
        public DateTime DateUpdated { get; set; }
        public DateTime LastLogin{ get; set; }

    }

In _LoginPartial I would like to get the Name, instead of the UserName which it gets by default

@using Microsoft.AspNetCore.Identity
@using RioTintoQRManager.Models

@inject SignInManager<ApplicationUser> SignInManager
@inject UserManager<ApplicationUser> UserManager
@if (SignInManager.IsSignedIn(User))
{
     @UserManager.GetUserName(User)
}

How do I extend the UserManager, or create a new method that would be available in the view like UserManager.GetUserName is?