Q: Best practice MediatR in a console application?

Hello,

It is my understanding that it is not straight forward to go from ASP.NET Core to a Console application as ASP.NET Core handles the scope creation, for example, to use a DbContext in MediatR. I have read about MediatR and Dependency Injection in .NET Core and I am trying to figure out how to properly implement the following in a console application. “A small menu and a request to MediatR for every option to execute queries in a DbContext.”

Here is what I have working for now. I am just wondering if it is considered best practices or if there is a better way to do it?

Program.cs

public static class Program
{
    public static async Task Main(string[] args)
    {
        var hostBuilder = CreateHostBuilder(args);

        await hostBuilder.RunConsoleAsync();
    }

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureServices((hostingContext, services) =>
            {
                services.AddDbContext<MyDbContext>(options =>
                    options.UseSqlServer(configuration.GetConnectionString("MyDatabase")));

                services.AddScoped<IMyDbContext>(provider => provider.GetService<MyDbContext>());
                services.AddMediatR(Assembly.GetExecutingAssembly());
                services.AddSingleton<IHostedService, ConsoleApp>();
            });
}

ConsoleApp.cs

public class ConsoleApp : IHostedService
{
    private readonly ILogger _logger;
    private readonly IServiceScopeFactory _serviceScopeFactory;
    public ConsoleApp(ILogger<ConsoleApp> logger, IServiceScopeFactory serviceScopeFactory)
    {
        _logger = logger;
        _serviceScopeFactory = serviceScopeFactory;
    }
    
    public async Task StartAsync(CancellationToken cancellationToken)
    {
        _logger.LogInformation("Starting application");
        int choice = -1;
        while (choice != 0)
        {
            WriteLine("Please choose one of the following options:");
            WriteLine("0. Exit");
            WriteLine("1. Extract receipts");
            WriteLine("2. Upload receipts");

            try
            {
                choice = int.Parse(ReadLine());
            }
            catch (FormatException)
            {
                choice = -1;
            }

            switch (choice)
            {
                case 0:
                    WriteLine("Bye...");
                    break;
                case 1:
                    using (var scope = _serviceScopeFactory.CreateScope())
                    {
                        var _mediator = scope.ServiceProvider.GetRequiredService<IMediator>();
                       
                        await _mediator.Send(new ExtractReceiptsCommand(), cancellationToken);
                    }
                    break;
                case 2:
                    using (var scope = _serviceScopeFactory.CreateScope())
                    {
                        var _mediator = scope.ServiceProvider.GetRequiredService<IMediator>();

                        await _mediator.Send(new UploadReceiptsCommand(), cancellationToken);
                    }
                    break;
                default:
                    WriteLine("Invalid choice! Please try again.");
                    break;
            }
        }
    }
}

Then I inject IMyDbContext inside the request handler constructor and everything looks like it is working properly. Thank you for your suggestions.

[lilasquared]

MediatR shouldn’t care whether you’re in a web context or a console context so long as the DI is all hooked up which it looks like you have done here.

[Pyrobolser]

@lilasquared That’s exactly what I’m trying to do.

@jbogard I’ll try to look into it, let me know if you know of an example that lies somewhere that I could look at. If you happen to add some details about Console app I’ll be sure to check it out too.

Thank you both for your help.