.NET Aspire helps manage applications, services (such as Redis), and other project dependencies. It also provides a dashboard for monitoring. Aspire consists of two main components: AppHost and ServiceDefaults.

AppHost is the orchestration project where we manage the referenced services. Projects can be added as follows:

[program.cs]

var builder = DistributedApplication.CreateBuilder(args);

var projectA = builder.AddProject<Projects.ProjectA>("serviceA").WithExternalHttpEndpoints();

builder.AddProject<Projects.ProjectB>("serviceB")
    .WithExternalHttpEndpoints()
    .WithReference(projectA)
    .WaitFor(projectA);

builder.Build().Run();

In the example above, two service projects are added. Using extensions, we can configure various settings and behaviors for these projects.

Once the AppHost project starts, all referenced projects will automatically launch, eliminating the need to start them manually.

After AppHost is running, the dashboard becomes available. The dashboard allows us to view the added projects and monitor their details (telemetry, etc.), which are provided through the ServiceDefaults module.

ServiceDefaults provides extensions that can be used in the added projects. These extensions collect project-related data, which AppHost utilizes to display information on the dashboard. Extension can be used as follows:

[program.cs]

var builder = WebApplication.CreateBuilder(args);

builder.AddServiceDefaults(); // #1

...

var app = builder.Build();

...

app.MapDefaultEndpoints(); // #2

app.Run();

To create a new Aspire project, you can use the following command:

dotnet new aspire

If you want to add Aspire to an existing project, modify the .csproj file of a Web API project as follows to designate it as an AppHost project:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <IsAspireHost>true</IsAspireHost>
    ...
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Aspire.Hosting.AppHost" />
    ...
  </ItemGroup>

</Project>

The AppHost project also requires a class library project(ServiceDefaults projects). Create a new class library and update its .csproj file as follows:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <IsAspireSharedProject>true</IsAspireSharedProject>
  </PropertyGroup>

  <ItemGroup>
    <FrameworkReference Include="Microsoft.AspNetCore.App" />

    <!-- These dependencies are optional and can be adjusted as needed. -->
    <PackageReference Include="Microsoft.Extensions.Http.Resilience" />
    <PackageReference Include="Microsoft.Extensions.ServiceDiscovery" />
    <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" />
    <PackageReference Include="OpenTelemetry.Extensions.Hosting" />
    <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" />
    <PackageReference Include="OpenTelemetry.Instrumentation.Http" />
    <PackageReference Include="OpenTelemetry.Instrumentation.Runtime" />
  </ItemGroup>

</Project>

If you encounter the error ASPIRE006 SDK error while adding Aspire to an existing project, update the .csproj file to specify the correct SDK version:

<Sdk Name="Aspire.AppHost.Sdk" Version="9.0.0" />

The Aspire dashboard provides a live interface for monitoring telemetry data, viewing logs, and starting or stopping projects in real time.