Minimal aspnet mvc app.cs

using System.ComponentModel.DataAnnotations;
using System.Net;
using AutoMapper;
using AutoMapper.QueryableExtensions;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddSwaggerGen();
builder.Services.AddControllers();
builder.Services.AddDbContext<TodoDbContext>(cfg => cfg.UseInMemoryDatabase("DbName"));
builder.Services.AddAutoMapper(typeof(TodoModel).Assembly);

var app = builder.Build();

app.UseSwagger();
app.UseSwaggerUI();
app.MapControllers();
app.Run();

public class TodoModel // Slim DTO for http transfer
{
    public int Id { get; set; }

    public string TaskName { get; set; }
}

public class TodoModelMappingProfile : Profile // This class define how to map object of type Todo to object of type TodoModel
{
    public TodoModelMappingProfile()
    {
        CreateMap<Todo, TodoModel>()
            .ForMember(t => t.TaskName, opt => opt.MapFrom(t => t.Name)); // We tell that TaskName should be taken from Name column
    }
}

public class Todo // Entity & model at the same time
{
    [Key] public int Id { get; set; }

    [Required] [MaxLength(128)] public string Name { get; set; }

    public bool Completed { get; set; }
}

public class TodoDbContext : DbContext // Database information - what models should be tables and so on
{
    public DbSet<Todo> Todos { get; set; }

    public TodoDbContext(DbContextOptions options) : base(options)
    {
    }
}

[ApiController]
public class TodoController : Controller // Endpoint to process http requests
{
    private readonly TodoDbContext _dbContext;
    private readonly IMapper _mapper;

    public TodoController(TodoDbContext dbContext, IMapper mapper)
    {
        _dbContext = dbContext;
        _mapper = mapper;
    }

    [HttpGet]
    [Route("todos/{id}")]
    [ProducesResponseType(typeof(TodoModel), (int)HttpStatusCode.OK)]
    public async Task<IActionResult> Get(int id, CancellationToken token)
    {
        var todo = await _dbContext.Todos.ProjectTo<TodoModel>(_mapper.ConfigurationProvider).FirstOrDefaultAsync(t => t.Id == id, token);
        return todo == null ? NotFound() : Ok(todo);
    }

    [HttpPost]
    [Route("todos")]
    [ProducesResponseType(typeof(Todo), (int)HttpStatusCode.OK)]
    public async Task<IActionResult> Create(Todo request, CancellationToken token)
    {
        await _dbContext.Todos.AddAsync(request, token);
        await _dbContext.SaveChangesAsync(token);
        return Ok(request);
    }
}