✅ Understanding how to create a controller in ASP.NET.

// Category.cs 
namespace FAQ.Models
{
    public class Category
    {
        // Entities are rows in a C# database. 
        public required string CategoryId { get; set; }
        public required string Name { get; set; }
        public required int FAQID { get; set; }

        public required int TopicID { get; set; }
    }

    // make a category constructor and on model builder
}

// FAQ.CS
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Internal;
using FAQ.Models; 

namespace FAQ.Models
{
    public class QuestionAnswer
    {
        public required int  Id {get; set;}                            
        public required string  Question {get; set;} 
        public required string Answer { get; set; }
        public required string TopicId { get; set; } = null!;
        public Topic Topic { get; set; } = null!;
        public required string CategoryId { get; set; } = null!;
        public Category Category { get; set; } = null!;        
    }
}

namespace FAQ.Models;

public class ErrorViewModel
{
    public string? RequestId { get; set; }

    public bool ShowRequestId => !string.IsNullOrEmpty(RequestId);
}

// TopicModel.cs 
namespace FAQ.Models

{
    public class Topic
    {
        // must be a string per instructions
        public required string Id { get; set; }
        public required string Name { get; set; }
    }

    // make a topic constructor and on model builder
    // public FAQModel() { } // EF-friendly parameterless ctor

    //  protected void OnModelCreating(ModelBuilder modelBuilder)
}