ASP.NET/ProjectOrientedSessions/Session04/Session04 Backend.md

🛠️ Task Checklist

Preparation:

The unedited conversation with Chat GPT, concerning almost all of the aspects of this session: (optional): read this to get a better understanding of the topic: https://chatgpt.com/share/67f18460-1c1c-8010-bc57-9f3b683ec87a

🚧Branching

•  Create the feature/transportation-search branch based on develop

DTO

In order to develop transportation search flow, three DTOs need to be created in the application layer.

•  Create DTOs related to transportation search flow 📂 Suggested Folder: Application/DTOs/City`

public class CityDto
{
    public int Id { get; init; }
    public required string Title { get; init; }
}

📂 Suggested Folder: Application/DTOs/Transportation

public class TransportationSearchRequestDto
{
     public short? VehicleTypeId { get; init; }
public int? FromCityId { get; init; }
public int? ToCityId { get; init; }
public DateTime? StartDate { get; init; }
public DateTime? EndDate { get; init; }

public class TransportationSearchResultDto
{
    public long Id { get; init; }
public int VehicleTypeId { get; init; }   
public string? VehicleTitle { get; init; }   
public required string CompanyTitle { get; init; }   
public required string FromLocationTitle { get; init; }
public required string ToLocationTitle { get; init; }
public required string FromCityTitle { get; init; }
public required string ToCityTitle { get; init; }
public DateTime StartDateTime { get; init; }
public DateTime? EndDateTime { get; init; }
public decimal Price { get; init; }
public int RemainingCapacity { get; init; }

Repository

There are a few things to be add to some repositories for transportation search flow.

• Create DTOs related to transportation search flow

📂 Suggested Folder: Domain/Framework/Interfaces/Repositories/ TransportationRepositories

public interface ITransportationRepository : IRepository<Transportation, long>
{
    Task<IEnumerable<Transportation>> SearchTransportationsAsync(
	    short? vehicleTypeId,
        int? fromCityId,
        int? toCityId, 
        DateTime? startDate, 
        DateTime? endDate);
}

📂 Suggested Folder: Infrastructure/Services/Services/TransportationRepositories

public class TransportationRepository :
        BaseRepository<ApplicationDBContext, Transportation, long>,
        ITransportationRepository
    {
        public TransportationRepository(ApplicationDBContext dbContext) : base(dbContext)
        {

        }

        public async Task<IEnumerable<Transportation>> SearchTransportationsAsync(
            short? vehicleTypeId,
            int? fromCityId,
            int? toCityId,
            DateTime? startDate,
            DateTime? endDate)
        {
            var query = DbContext.Transportations
                .Include(x => x.Vehicle)
                .Include(x => x.FromLocation).ThenInclude(x => x.City)
                .Include(x => x.ToLocation).ThenInclude(x => x.City)
                .Include(x => x.Company)
                .AsQueryable();
            query = query.Where(x => vehicleTypeId == null || x.Vehicle.VehicleTypeId == vehicleTypeId.Value);
            query = query.Where(x => fromCityId == null || x.FromLocation.CityId == fromCityId.Value);
            query = query.Where(x => toCityId == null || x.ToLocation.CityId == toCityId.Value);
            query = query.Where(x => startDate == null || x.StartDateTime.Date == startDate.Value.Date);
            query = query.Where(x => endDate == null || (x.EndDateTime.HasValue && x.EndDateTime.Value == endDate.Value.Date));
            
            return await query.ToListAsync();
        }
    }

Auto Mapper

Auto Mapper simplifies mapping between aggregates and DTOs in both directions.

• Create a MappingProfile that inherits Profile, and use it to add configurations for mappings

📂 Suggested Folder: Application/Mappers/Profiles

public class MappingProfile : Profile
{
    public MappingProfile()
    {
        CreateMap<Transportation, TransportationSearchResultDto>()
            .ForMember(dest => dest.CompanyTitle, 
            opt => opt.MapFrom(src => src.Company.Title))
            
            .ForMember(dest => dest.FromLocationTitle, 
            opt => opt.MapFrom(src => src.FromLocation.Title))
            
            .ForMember(dest => dest.ToLocationTitle, 
            opt => opt.MapFrom(src => src.ToLocation.Title))
            
            .ForMember(dest => dest.FromCityTitle, 
            opt => opt.MapFrom(src => src.FromLocation.City.Title))
            
             .ForMember(dest => dest.ToCityTitle, 
             opt => opt.MapFrom(src => src.ToLocation.City.Title));

        CreateMap<City, CityDto>();
        }
    }

• Register AutoMapper config file in Program.cs

 .
 .
 .

 builder.Services.AddAutoMapper(typeof(MappingProfile));
 
 var app = builder.Build();

 .
 .
 .

Result & Result Status

• Create ResultStatus enum and Result class 📂 Suggested Folder: Application/Result

Result is a template to transfer data between services and controllers (in backend), so will use a generic type

public class Result<T>
{
	public ResultStatus Status { get; set; }
	public string? ErrorMessage { get; set; }
	public T? Data { get; set; }
	public bool IsSuccess => Status == ResultStatus.Success;

	public static Result<T> Success(T data)
	{
		return new Result<T>
		{
			Status = ResultStatus.Success,
			Data = data
		};
	}

	public static Result<T> Error(T data)
	{
		return new Result<T>
		{
			Status = ResultStatus.Error,
			Data = data
		};
	}

	public static Result<T> NotFound(T data)
	{
		return new Result<T>
		{
			Status = ResultStatus.NotFound,
			Data = data
		};
	}
}

As you can see, there's a property of type ResultStatus, which is a enum for status of request

public enum ResultStatus
{
	Success,
	NotFound,
	ValidationError,
	Conflict,
	Unauthorized,
	Forbidden,
	Error
}

You can read more about enums: W3Schools

IService & Service

Now, use I[Entity]Repositry and IUnitOfWork in services to implement business logic

• Create I[Entity]Service and [Entity]Service which implements it

📂 Suggested Folder for I[Entity]Service: Application/Interfaces

📂 Suggested Folder for Services: Application/Services

• existence of an interface for each service class is optional
• services can have multiple repositories in them -> logic-based structure

An example of I[Entity]Service:

public interface ITransportationService
{
    Task<Result<IEnumerable<TransportationSearchResultDto>>> SearchTransportationsAsync(TransportationSearchRequestDto searchRequest);
}

An example of [Entity]Service:

public class TransportationService : ITransportationService
{
	private readonly ITransportationRepository _transportationRepository;
	private readonly IMapper _mapper;
	private readonly IUnitOfWork _unitOfWork;

	public TransportationService(ITransportationRepository transportationRepository, IMapper mapper, IUnitOfWork unitOfWork)
	{
		_transportationRepository = transportationRepository;
		_mapper = mapper;
		_unitOfWork = unitOfWork;
	}

	public async Task<Result<IEnumerable<TransportationSearchResultDto>>> SearchTransportationsAsync(TransportationSearchRequestDto requestDto)
	{
		var result = await _transportationRepository.SearchTransportationsAsync(
			vehicleTypeId: requestDto.VehicleTypeId,
			fromCityId: requestDto.FromCityId,
			toCityId: requestDto.ToCityId,
			startDateTime: requestDto.StartDate,
			endDateTime: requestDto.EndDate);

		if (result.Any())
		{
			var dto = _mapper.Map<IEnumerable<TransportationSearchResultDto>>(result);
			return Result<IEnumerable<TransportationSearchResultDto>>.Success(dto);
		}

		return Result<IEnumerable<TransportationSearchResultDto>>.NotFound(null);
	}
}

• Register services in Program.cs:

.
.
.
builder.Services.AddScoped<ITransportationService, TransportationService>();
builder.Services.AddScoped<ICityService, CityService>();
.
.
.

Controller

Now we're getting to endpoints, you should communicate with client side through web-api. So every controller uses Services in Application layer to receive requests and send responses with DTOs.

• Create an APIController (right click on the folder, and then under Add, select Controller, and then make sure to select the APIController type) 📂 Suggested Folder: WebAPI/Controller

You should use [ApiController] attribute on top of them, route them and handle different status codes. TransportationController:

[ApiController]
[Route("api/[controller]")]
public class TransportationController : ControllerBase
{
	private readonly ITransportationService _transportationService;

	public TransportationController(ITransportationService transportationService)
	{
		_transportationService = transportationService;
	}

	[HttpGet("search")]
	public async Task<IActionResult> SearchTransportations([FromQuery] TransportationSearchRequestDto searchRequest)
	{
		if (searchRequest == null)
		{
			return BadRequest("Invalid search request");
		}

		var result = await _transportationService.SearchTransportationsAsync(searchRequest);
		if (result.IsSuccess)
		{
			return Ok(result);
		}

		// any unsuccessful status
		return result.Status switch
		{
			ResultStatus.NotFound => NotFound(result.ErrorMessage),
			ResultStatus.ValidationError => BadRequest(result.ErrorMessage),
			_ => StatusCode(500, result.ErrorMessage),
		};
	}
}

• HttpGet: handles a GET request from client -> important for routing
• Ok, BadRequest, NotFound and StatusCode are json results to send through API
• Use TransportationService to communicate with Application

Inserting Sample Data

For testing purposes, add some data into the related tables. You are provided with a SQL script, that adds some sample data into the following tables

Important Notes: Note that different database names, and different table names will produce errors while executing the script. Consider adjusting these names before executing the script

• Cities

• Companies

• LocationTypes

• Locations

• VehicleTypes

• Vehicles

• Transportation

• Open TransportationRelatedSampleData.sql with SSMS, and execute the query

Note: there has been changes in database structure since this note and this file has been written.

🚧Merge

• Create a PR and merge the current branch with develop

🧠 Hints & Notes

🙌 Acknowledgements

• ChatGPT for snippet refinement and explanations

🔍 References