C#•11mo ago

Implementing MediatR

How can i implement MediatR library to redirect the request relevant Service class (like GenerateCodeService, CreateProductService) And i don't wanna use CQRS pattern

35 Replies

Pobiega•11mo ago

Makes no sense to use mediatr or similar if you're gonna use service classes anyways MediatR works fine without an explicit CQRS split (commands vs queries), but it still relies heavily on the idea that a request has a handler

baristanerOP•11mo ago

My folder structure for this thing is like this

|-- Features
|   |-- Products
|       |-- Add
|           |-- AddProductCommand.cs
|           |-- AddProductCommandHandler.cs
|           |-- Validators
|               |-- ProductValidator.cs

|-- Features
|   |-- Products
|       |-- Add
|           |-- AddProductCommand.cs
|           |-- AddProductCommandHandler.cs
|           |-- Validators
|               |-- ProductValidator.cs

ProductService.cs

c#
using fastwin.Entities;
using fastwin.Interfaces;
using FluentValidation;
using System.Diagnostics;

namespace fastwin.Services
{
    public class ProductService
    {
        private readonly IRepository<Product> _productRepository;
        private readonly IValidator<Product> _productValidator;

        public ProductService(IRepository<Product> productRepository, IValidator<Product> productValidator)
        {
            _productRepository = productRepository;
            _productValidator = productValidator;
        }

        public async Task<Product> AddProductAsync(Product product)
        {
            try
            {
                await _productValidator.ValidateAndThrowAsync(product);
                await _productRepository.AddAsync(product);
                Debug.WriteLine("Product added successfully in the service.");
                return product;
            }
            catch (ValidationException ex)
            {
                Debug.WriteLine($"Validation failed: {ex.Message}");
                throw; // Rethrow the exception to propagate it up
            }
            catch (Exception ex)
            {
                Debug.WriteLine($"Error adding product: {ex.Message}");
                throw; // Rethrow the exception to propagate it up
            }
        }



    }
}

c#
using fastwin.Entities;
using fastwin.Interfaces;
using FluentValidation;
using System.Diagnostics;

namespace fastwin.Services
{
    public class ProductService
    {
        private readonly IRepository<Product> _productRepository;
        private readonly IValidator<Product> _productValidator;

        public ProductService(IRepository<Product> productRepository, IValidator<Product> productValidator)
        {
            _productRepository = productRepository;
            _productValidator = productValidator;
        }

        public async Task<Product> AddProductAsync(Product product)
        {
            try
            {
                await _productValidator.ValidateAndThrowAsync(product);
                await _productRepository.AddAsync(product);
                Debug.WriteLine("Product added successfully in the service.");
                return product;
            }
            catch (ValidationException ex)
            {
                Debug.WriteLine($"Validation failed: {ex.Message}");
                throw; // Rethrow the exception to propagate it up
            }
            catch (Exception ex)
            {
                Debug.WriteLine($"Error adding product: {ex.Message}");
                throw; // Rethrow the exception to propagate it up
            }
        }



    }
}

ProductValidator.cs

c#
using fastwin.Entities;
using FluentValidation;

namespace fastwin.Features.Products.Add.Validators
{
    public class ProductValidator : AbstractValidator<Product>
    {
        public ProductValidator()
        {
            RuleFor(x => x.Name)
                .NotEmpty().WithMessage("Product Name is required.")
                .MaximumLength(3)
                .WithMessage("Product Name Only Can Be 3 Characters Length");

            RuleFor(product => product.Category)
                .Must(BeAValidEnumValue)
                .WithMessage("Invalid Category, please provide a valid category name.");
        }

        private bool BeAValidEnumValue(Category category)
        {
            return Enum.IsDefined(typeof(Category), category);
        }
    }
}

c#
using fastwin.Entities;
using FluentValidation;

namespace fastwin.Features.Products.Add.Validators
{
    public class ProductValidator : AbstractValidator<Product>
    {
        public ProductValidator()
        {
            RuleFor(x => x.Name)
                .NotEmpty().WithMessage("Product Name is required.")
                .MaximumLength(3)
                .WithMessage("Product Name Only Can Be 3 Characters Length");

            RuleFor(product => product.Category)
                .Must(BeAValidEnumValue)
                .WithMessage("Invalid Category, please provide a valid category name.");
        }

        private bool BeAValidEnumValue(Category category)
        {
            return Enum.IsDefined(typeof(Category), category);
        }
    }
}

AddProductCommand.cs

c#
using fastwin.Requests;
using MediatR;

public class AddProductCommand : IRequest<Unit>
{
    public ProductRequestDto ProductDto { get; }

    public AddProductCommand(ProductRequestDto productDto)
    {
        ProductDto = productDto;
    }
}

c#
using fastwin.Requests;
using MediatR;

public class AddProductCommand : IRequest<Unit>
{
    public ProductRequestDto ProductDto { get; }

    public AddProductCommand(ProductRequestDto productDto)
    {
        ProductDto = productDto;
    }
}

Pobiega•11mo ago

Your structure doesnt include a ProductService.cs

baristanerOP•11mo ago

It does but i just didn't sent it

Pobiega•11mo ago

if you just rename your "service" to AddProductCommandHandler you're doing things correctly.

baristanerOP•11mo ago

The thing is wait i'll explain

Pobiega•11mo ago

do not mix and match services with command handlers. thats just silly.

baristanerOP•11mo ago

AddProductCommandHandler.cs

c#
using fastwin.Entities;
using fastwin.Requests;
using fastwin.Services;
using MediatR;

public class AddProductCommandHandler : IRequestHandler<AddProductCommand, Unit>
{
    private readonly ProductService _productService;

    public AddProductCommandHandler(ProductService productService)
    {
        _productService = productService;
    }

    public async Task<Unit> Handle(AddProductCommand request, CancellationToken cancellationToken)
    {
        var product = ConvertToProduct(request.ProductDto);

        _productService.AddProductAsync(product);


        return Unit.Value;
    }

    private Product ConvertToProduct(ProductRequestDto productRequest)
    {
        return new Product
        {
            Name = productRequest.Name,
            Description = productRequest.Description,
            Category = Enum.Parse<Category>(productRequest.Category),
        };
    }
}

c#
using fastwin.Entities;
using fastwin.Requests;
using fastwin.Services;
using MediatR;

public class AddProductCommandHandler : IRequestHandler<AddProductCommand, Unit>
{
    private readonly ProductService _productService;

    public AddProductCommandHandler(ProductService productService)
    {
        _productService = productService;
    }

    public async Task<Unit> Handle(AddProductCommand request, CancellationToken cancellationToken)
    {
        var product = ConvertToProduct(request.ProductDto);

        _productService.AddProductAsync(product);


        return Unit.Value;
    }

    private Product ConvertToProduct(ProductRequestDto productRequest)
    {
        return new Product
        {
            Name = productRequest.Name,
            Description = productRequest.Description,
            Category = Enum.Parse<Category>(productRequest.Category),
        };
    }
}

ProductController.cs

c#
namespace fastwin.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class ProductController : ControllerBase
    {
        private readonly IMediator _mediator;

        public ProductController(IMediator mediator)
        {
            _mediator = mediator;
        }

        [HttpPost("add-product")]
        public async Task<IActionResult> AddProduct([FromBody] ProductRequestDto productDto)
        {
            try
            {
                var result = await _mediator.Send(new AddProductCommand(productDto));

                return Ok(result);
            }
            catch (Exception ex)
            {
                return StatusCode(500, $"Internal server error: {ex.Message}");
            }
        }
    }
}

c#
namespace fastwin.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class ProductController : ControllerBase
    {
        private readonly IMediator _mediator;

        public ProductController(IMediator mediator)
        {
            _mediator = mediator;
        }

        [HttpPost("add-product")]
        public async Task<IActionResult> AddProduct([FromBody] ProductRequestDto productDto)
        {
            try
            {
                var result = await _mediator.Send(new AddProductCommand(productDto));

                return Ok(result);
            }
            catch (Exception ex)
            {
                return StatusCode(500, $"Internal server error: {ex.Message}");
            }
        }
    }
}

It returns ok but it's empty and it gives this error on console

fail: Microsoft.EntityFrameworkCore.Database.Connection[20004]
      An error occurred using the connection to database 'CodeGeneratorDB' on server 'TR-ADN-B5CN4D3\SQLEXPRESS01'.
fail: 1/4/2024 16:12:26.592 RelationalEventId.ConnectionError[20004] (Microsoft.EntityFrameworkCore.Database.Connection)
      An error occurred using the connection to database 'CodeGeneratorDB' on server 'TR-ADN-B5CN4D3\SQLEXPRESS01'.

fail: Microsoft.EntityFrameworkCore.Database.Connection[20004]
      An error occurred using the connection to database 'CodeGeneratorDB' on server 'TR-ADN-B5CN4D3\SQLEXPRESS01'.
fail: 1/4/2024 16:12:26.592 RelationalEventId.ConnectionError[20004] (Microsoft.EntityFrameworkCore.Database.Connection)
      An error occurred using the connection to database 'CodeGeneratorDB' on server 'TR-ADN-B5CN4D3\SQLEXPRESS01'.

But i'm %100 sure that my db connection string works Because it works on other endponits

Pobiega•11mo ago

You are overengineering this massively. And using generic repositories over EF Core is redudant and bad practice. Sounds odd that EF would throw that error if the connection worked, so I can only guess that its related to your service lifetime?

baristanerOP•11mo ago

How can i simplify this like as i said my supervisor asked me to "implement MediatR library to redirect the request relevant Service class (like GenerateCodeService, CreateProductService)"

Pobiega•11mo ago

You did not say that, fyi. This is the first time you mentioned a supervisor or being ordered to do something this way. Still, this is an anti-pattern. But other than being a bad pattern, I don't see any obvious problems in the code you have shared that would explain why EF can't connect specifically for this endpoint.

baristanerOP•11mo ago

She also said Injecting repositories into the controller directly is not suitable. We can build a new structure like this: Controller > Service Class > Repository I mean that works like a charm But when i tried to use MediatR library to redirect the request relevant Service class it's so messy So i'm stuck...

Pobiega•11mo ago

That part is correct, you should not have business logic in a controller. What Im trying to get across is that you are doubling up on the intermediate layer.

Pobiega•11mo ago

Pobiega•11mo ago

this is what it should look like

baristanerOP•11mo ago

So do you suggest should i remove all the Features folder use service instead

Pobiega•11mo ago

and this is what you are doing

baristanerOP•11mo ago

And bytw i'm not working on a real project this is my internship assessment

Pobiega•11mo ago

I actually suggest skipping the Services layer, as thats the least useful comand handlers are almost the exact same thing, but more granular services are just multiple handlers grouped together for no purpose so skip the service, use the handlers. figure out why your database isnt working

baristanerOP•11mo ago

it is kinda odd error is this the correct way to inject mediart? Program.cs

c#
builder.Services.AddMediatR(cfg => {
    cfg.RegisterServicesFromAssembly(typeof(Program).Assembly);
});

c#
builder.Services.AddMediatR(cfg => {
    cfg.RegisterServicesFromAssembly(typeof(Program).Assembly);
});

Pobiega•11mo ago

seems fine yeah assuming all your handlers are actually in that assembly

baristanerOP•11mo ago

Here is my full program.cs

c#
using fastwin;
using Microsoft.EntityFrameworkCore;
using fastwin.Repository.Repositories;
using fastwin.Interfaces;
using FastWIN.API.Converters;
using FluentValidation.AspNetCore;
using FluentValidation;
using fastwin.Services;
using fastwin.Features.Products.Add.Validators;
using System.Reflection;
using MediatR;
using Microsoft.AspNetCore.Hosting;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers()
.AddJsonOptions(options =>
{
  options.JsonSerializerOptions.Converters.Add(new JsonDateTimeConverter());
});

builder.Services.AddFluentValidationAutoValidation()
    .AddFluentValidationClientsideAdapters()
    .AddValidatorsFromAssemblyContaining<ProductValidator>();


builder.Services.AddMediatR(cfg => {
    cfg.RegisterServicesFromAssembly(typeof(Program).Assembly);
});

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();



builder.Services.AddDbContext<CodeDbContext>(options =>
{
    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection"))
           .LogTo(Console.WriteLine, LogLevel.Information); 
});


builder.Services.AddScoped(typeof(IRepository<>), typeof(GenericRepository<>));
builder.Services.AddScoped<ProductService>();


var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment() || app.Environment.IsProduction())
{
    app.UseDeveloperExceptionPage();
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseCors(builder => builder
.AllowAnyOrigin()
.AllowAnyMethod()
.AllowAnyHeader()
);



app.UseAuthorization();

app.MapControllers();

app.Run();

c#
using fastwin;
using Microsoft.EntityFrameworkCore;
using fastwin.Repository.Repositories;
using fastwin.Interfaces;
using FastWIN.API.Converters;
using FluentValidation.AspNetCore;
using FluentValidation;
using fastwin.Services;
using fastwin.Features.Products.Add.Validators;
using System.Reflection;
using MediatR;
using Microsoft.AspNetCore.Hosting;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers()
.AddJsonOptions(options =>
{
  options.JsonSerializerOptions.Converters.Add(new JsonDateTimeConverter());
});

builder.Services.AddFluentValidationAutoValidation()
    .AddFluentValidationClientsideAdapters()
    .AddValidatorsFromAssemblyContaining<ProductValidator>();


builder.Services.AddMediatR(cfg => {
    cfg.RegisterServicesFromAssembly(typeof(Program).Assembly);
});

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();



builder.Services.AddDbContext<CodeDbContext>(options =>
{
    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection"))
           .LogTo(Console.WriteLine, LogLevel.Information); 
});


builder.Services.AddScoped(typeof(IRepository<>), typeof(GenericRepository<>));
builder.Services.AddScoped<ProductService>();


var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment() || app.Environment.IsProduction())
{
    app.UseDeveloperExceptionPage();
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseCors(builder => builder
.AllowAnyOrigin()
.AllowAnyMethod()
.AllowAnyHeader()
);



app.UseAuthorization();

app.MapControllers();

app.Run();

Pobiega•11mo ago

new JsonDateTimeConverter()? is this .net 6? also, I personally prefer the services.AddMediatR(cfg => cfg.RegisterServicesFromAssemblyContaining<Startup>()); syntax but they do the same thing

baristanerOP•11mo ago

nope 8.0

Pobiega•11mo ago

then you shouldn't need that line STJ has full support for DateOnly and TimeOnly since .net 7

baristanerOP•11mo ago

It didn't convert datetime utc to json

Pobiega•11mo ago

? DateTimeOffset? it absolutely supports that, even since .net 5

baristanerOP•11mo ago

btw my validators also not working

Pobiega•11mo ago

and if you are using anything other than DateTimeOffset, you are doing something wrong DateTime for example should never be used

baristanerOP•11mo ago

Honestly Wait i just clicked execute again and sql worked first time it didnt

Pobiega•11mo ago

why are you using sqlexpress anyways please use a more appropriate database. sqlserver, postgres, sqlite...

baristanerOP•11mo ago

It creates the product in db but
Response body is {}

Pobiega•11mo ago

well.. uh.. yes?

return Unit.Value;

return Unit.Value;

your command returns Unit lol Unit is MediatRs version of void, aka nothing so this is a comand that has no return value

baristanerOP•11mo ago

oh yeah sorry i'm kinda new

Gaming

Programming

Implementing MediatR