Dependency Injection

INFO

Remember that you can download the samples from the GitHub repository.

This sample makes use of Shuttle.Esb.AzureStorageQueues for the message queues. Local Azure Storage Queues should be provided by Azurite.

Once you have opened the Shuttle.DependencyInjection.sln solution in Visual Studio set the following projects as startup projects:

• Shuttle.DependencyInjection.Client
• Shuttle.DependencyInjection.Server

Implementation

Since .NET provides a production-ready dependency injection framework, this sample will demonstrate a very simple use-case.

In this guide we'll create the following projects:

• Shuttle.DependencyInjection.Client (Console Application)
• Shuttle.DependencyInjection.Server (Console Application)
• Shuttle.DependencyInjection.EMail (Class Library)
• Shuttle.DependencyInjection.Messages (Class Library)

Messages

Create a new class library called Shuttle.DependencyInjection.Messages with a solution called Shuttle.DependencyInjection

Note: remember to change the Solution name.

RegisterMember

Rename the Class1 default file to RegisterMember and add a UserName property.

nnamespace Shuttle.DependencyInjection.Messages;

public class RegisterMember
{
    public string UserName { get; set; } = string.Empty;
}

Client

Add a new Console Application to the solution called Shuttle.DependencyInjection.Client.

Install the Shuttle.Esb.AzureStorageQueues nuget package.

This will provide access to the Azure Storage Queues IQueue implementation and also include the required dependencies.

Install the Microsoft.Extensions.Configuration.Json nuget package.

This will provide the ability to read the appsettings.json file.

Add a reference to the Shuttle.DependencyInjection.Messages project.

Program

Implement the main client code as follows:

using System;
using System.Threading.Tasks;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Shuttle.DependencyInjection.Messages;
using Shuttle.Esb;
using Shuttle.Esb.AzureStorageQueues;

namespace Shuttle.DependencyInjection.Client;

internal class Program
{
    private static async Task Main(string[] args)
    {
        var configuration = new ConfigurationBuilder()
            .AddJsonFile("appsettings.json").Build();

        var services = new ServiceCollection()
            .AddSingleton<IConfiguration>(configuration)
            .AddServiceBus(builder =>
            {
                configuration.GetSection(ServiceBusOptions.SectionName)
                    .Bind(builder.Options);
            })
            .AddAzureStorageQueues(builder =>
            {
                builder.AddOptions("azure", new()
                {
                    ConnectionString = "UseDevelopmentStorage=true;"
                });
            });

        Console.WriteLine("Type some characters and then press [enter] to submit; an empty line submission stops execution:");
        Console.WriteLine();

        await using (var serviceBus = await services.BuildServiceProvider()
                         .GetRequiredService<IServiceBus>().StartAsync())
        {
            string userName;

            while (!string.IsNullOrEmpty(userName = Console.ReadLine() ?? string.Empty))
            {
                await serviceBus.SendAsync(new RegisterMember
                {
                    UserName = userName
                });
            }
        }
    }
}

Client configuration file

Add an appsettings.json file as follows:

{
  "Shuttle": {
    "ServiceBus": {
      "MessageRoutes": [
        {
          "Uri": "azuresq://azure/shuttle-server-work",
          "Specifications": [
            {
              "Name": "StartsWith",
              "Value": "Shuttle.DependencyInjection.Messages"
            }
          ]
        }
      ]
    }
  }
}

This tells Shuttle.Esb that all messages that are sent and have a type name starting with Shuttle.DependencyInjection.Messages should be sent to endpoint azuresq://azure/shuttle-server-work.

E-Mail

To demonstrate the dependency injection we will create a fake e-mail service that we intend using in the server endpoint.

Add a new Class Library to the solution called Shuttle.DependencyInjection.EMail.

IEMailService

Add an interface called IEMailService and implement it as follows:

using System.Threading.Tasks;

namespace Shuttle.DependencyInjection.EMail;

public interface IEMailService
{
    Task SendAsync(string name);
}

EMailService

Rename the default Class1 file to EMailService and implement the IEMailService interfaces as follows:

using System;
using System.Threading.Tasks;

namespace Shuttle.DependencyInjection.EMail;

public class EMailService : IEMailService
{
    public async Task SendAsync(string name)
    {
        Console.WriteLine();
        Console.WriteLine("[SENDING E-MAIL] : name = '{0}'", name);
        Console.WriteLine();

        await Task.Delay(TimeSpan.FromSeconds(3)); // simulate communication wait time

        Console.WriteLine();
        Console.WriteLine("[E-MAIL SENT] : name = '{0}'", name);
        Console.WriteLine();
    }
}

Server

Add a new Console Application to the solution called Shuttle.DependencyInjection.Server.

Install the Shuttle.Esb.AzureStorageQueues nuget package.

This will provide access to the Azure Storage Queues IQueue implementation and also include the required dependencies.

Install the Microsoft.Extensions.Hosting nuget package.

This allows a console application to be hosted using the .NET generic host.

Install the Microsoft.Extensions.Configuration.Json nuget package.

This will provide the ability to read the appsettings.json file.

Add references to both the Shuttle.DependencyInjection.Messages and Shuttle.DependencyInjection.EMail projects.

Program

Implement the Program class as follows:

using System.Threading.Tasks;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Shuttle.Core.Contract;
using Shuttle.DependencyInjection.EMail;
using Shuttle.Esb;
using Shuttle.Esb.AzureStorageQueues;

namespace Shuttle.DependencyInjection.Server;

public class Program
{
    public static async Task Main()
    {
        await Host.CreateDefaultBuilder()
            .ConfigureServices(services =>
            {
                var configuration = new ConfigurationBuilder()
                    .AddJsonFile("appsettings.json").Build();

                services
                    .AddSingleton<IConfiguration>(configuration)
                    .AddSingleton<IEMailService, EMailService>()
                    .AddServiceBus(builder =>
                    {
                        configuration.GetSection(ServiceBusOptions.SectionName)
                            .Bind(builder.Options);
                    })
                    .AddAzureStorageQueues(builder =>
                    {
                        builder.AddOptions("azure", new()
                        {
                            ConnectionString = Guard.AgainstNullOrEmptyString(configuration.GetConnectionString("azure"))
                        });
                    });
            })
            .Build()
            .RunAsync();
    }
}

Server configuration file

Add an appsettings.json file as follows:

{
  "ConnectionStrings": {
    "azure": "UseDevelopmentStorage=true;"
  },
  "Shuttle": {
    "ServiceBus": {
      "Inbox": {
        "WorkQueueUri": "azuresq://azure/shuttle-server-work",
        "ErrorQueueUri": "azuresq://azure/shuttle-error"
      }
    }
  }
}

RegisterMemberHandler

Add a new class called RegisterMemberHandler that implements the IMessageHandler<RegisterMember> interface as follows:

using System;
using System.Threading.Tasks;
using Shuttle.Core.Contract;
using Shuttle.DependencyInjection.EMail;
using Shuttle.DependencyInjection.Messages;
using Shuttle.Esb;

namespace Shuttle.DependencyInjection.Server;

public class RegisterMemberHandler : IMessageHandler<RegisterMember>
{
    private readonly IEMailService _emailService;

    public RegisterMemberHandler(IEMailService emailService)
    {
        _emailService = Guard.AgainstNull(emailService);
    }

    public async Task ProcessMessageAsync(IHandlerContext<RegisterMember> context)
    {
        Console.WriteLine();
        Console.WriteLine($"[MEMBER REGISTERED] : user name = '{context.Message.UserName}'");
        Console.WriteLine();

        await _emailService.SendAsync(context.Message.UserName);

        await Task.CompletedTask;
    }
}

This will write out some information to the console window. The injected e-mail service will also be invoked and you'll see the result in the console window.

Run

Set both the client and server projects as the startup.

Execute

Execute the application.

The client application will wait for you to input a user name. For this example enter my user name and press enter:

INFO

You will notice that the server application has processed the message and simulated sending an e-mail though the IEMailService implementation.

You have now implemented dependency injection for message handlers.