Building a .NET Minimal API with AutoMapper

Introduction In this tutorial, I will walk you through creating a .NET minimal API that leverages AutoMapper for object-to-object mapping. We'll build an API endpoint for creating and returning coupon data.

Step 1: Setting Up the Project First, create a new .NET minimal API project and add the necessary AutoMapper packages:

dotnet add package AutoMapper --version 11.0.1
dotnet add package AutoMapper.Extensions.Microsoft.DependencyInjection --version 11.0.0

Step 2: Creating Models and DTOs Create the models and DTOs in your project.

Models/Coupon.cs:

namespace MagicVilla_CouponAPI.Models
{
    public class Coupon
    {
        public int Id { get; set; }
        public string Code { get; set; }
        public decimal Discount { get; set; }
        public DateTime ExpiryDate { get; set; }
    }
}

DTOs/CouponCreateDTO.cs:

namespace MagicVilla_CouponAPI.DTOs
{
    public class CouponCreateDTO
    {
        public string Code { get; set; }
        public decimal Discount { get; set; }
        public DateTime ExpiryDate { get; set; }
    }
}

DTOs/CouponDTO.cs:

namespace MagicVilla_CouponAPI.DTOs
{
    public class CouponDTO
    {
        public int Id { get; set; }
        public string Code { get; set; }
        public decimal Discount { get; set; }
        public DateTime ExpiryDate { get; set; }
    }
}

Step 3: Configuring AutoMapper Create a mapping configuration class to define the mappings.

MappingConfig.cs:

using AutoMapper;
using MagicVilla_CouponAPI.DTOs;
using MagicVilla_CouponAPI.Models;

namespace MagicVilla_CouponAPI
{
    public class MappingConfig : Profile
    {
        public MappingConfig()
        {
            CreateMap<Coupon, CouponCreateDTO>().ReverseMap();
            CreateMap<Coupon, CouponDTO>().ReverseMap();
        }
    }
}

Step 4: Configuring the API Configure AutoMapper and define the API endpoint in Program.cs.

Program.cs:

using AutoMapper;
using MagicVilla_CouponAPI;
using MagicVilla_CouponAPI.DTOs;
using MagicVilla_CouponAPI.Models;
using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddAutoMapper(typeof(MappingConfig));

var app = builder.Build();

// Configure the HTTP request pipeline.
app.MapPost("/api/coupon", (IMapper _mapper, CouponCreateDTO couponCreateDTO) =>
{
    Coupon coupon = _mapper.Map<Coupon>(couponCreateDTO);
    CouponDTO couponDTO = _mapper.Map<CouponDTO>(coupon);
    return Results.Ok(couponDTO);
});

app.Run();

12. Building a .NET Minimal API with AutoMapper