In the previous tutorial, we took a look at the basic sample Aspire web app works. This time, we’ll create a new app from scratch. This approach will help us get a better understanding of the basic building blocks of Aspire.
First, we create a new Aspire AppHost:
> dotnet new aspire-apphost -n SimpleApp-AppHost
The AppHost is the manager / orchestrator of the distributed application that we are building using the Aspire framework. Since it is an executable application, we can run it as soon as it is created. It will not do much, but does run:
> cd SimpleApp-AppHost<br>> dotnet run<br>Using launch settings from <redacted>\src\SimpleApp-AppHost\Properties\launchSettings.json...<br>Building...<br>info: Aspire.Hosting.DistributedApplication[0]<br> Aspire version: 8.2.2+5fa9337a84a52e9bd185d04d156eccbdcf592f74<br>info: Aspire.Hosting.DistributedApplication[0]<br> Distributed application starting.<br>info: Aspire.Hosting.DistributedApplication[0]<br> Application host directory is: <redacted>\src\SimpleApp-AppHost<br>info: Aspire.Hosting.DistributedApplication[0]<br> Now listening on: https://localhost:17114<br>info: Aspire.Hosting.DistributedApplication[0]<br> Login to the dashboard at https://localhost:17114/login?t=f3f0cf47ebc34c01d5214c2eb0d5cd18<br>info: Aspire.Hosting.DistributedApplication[0]<br> Distributed application started. Press Ctrl+C to shut down.
We can navigate to the dashboard, which is completely empty. But for me, working things are comforting, so this is good :-).
Turns out that adding a new application is not complicated at all. First thing that we need is create the service defaults project. This project defines the shared settings and configurations for the applications that run with the same host:
> dotnet new aspire-servicedefaults -n SimpleApp-ServiceDefaults
We will also create our web application:
> dotnet new web -n SimpleApp-Web1
There are a couple of “wires” that must be connected for these projects (settings, host, app) to work together. Applications that run with the host must reference the same service defaults project. The host needs to reference the applications. First, we’ll add a reference from the web app to the service defaults project:
> dotnet add .\SimpleApp-Web1\SimpleApp-Web1.csproj reference .\SimpleApp-ServiceDefaults\SimpleApp-ServiceDefaults.csproj
And then a reference from the host to the web app project:
> dotnet add .\SimpleApp-AppHost\SimpleApp-AppHost.csproj reference .\SimpleApp-Web1\SimpleApp-Web1.csproj
Two small code changes are needed to finish the job. First – add the defaults configuration to the web app for it to run on the Aspire host. This is done in the `Program.cs` file of the web app just after creating the builder:
var builder = WebApplication.CreateBuilder(args);
builder.AddServiceDefaults();
Finally the app project is added to the host builder so the host executes it. This is done in the `Program.cs` file of the app host project after creating the builder (promise next time to give better names to these files):
var builder = DistributedApplication.CreateBuilder(args);
builder.AddProject<Projects.SimpleApp_Web1>("Web1").WithExternalHttpEndpoints();
If you read this change carefully, you’ll notice that the name of the project is `SimpleApp_Web1` and not `SimpleApp-Web1`. This is because `C#` identifiers (and pretty sure most programming languages) don’t allow `-` as an identifier. Something to take into consideration when naming projects in the future.
Let’s run the host to see the results.
> dotnet run --project .\SimpleApp-AppHost\SimpleApp-AppHost.csproj
Using launch settings from .\SimpleApp-AppHost\Properties\launchSettings.json...
Building...
info: Aspire.Hosting.DistributedApplication[0]
Aspire version: 8.2.2+5fa9337a84a52e9bd185d04d156eccbdcf592f74
info: Aspire.Hosting.DistributedApplication[0]
Distributed application starting.
info: Aspire.Hosting.DistributedApplication[0]
Application host directory is: <redacted>\src\SimpleApp-AppHost
info: Aspire.Hosting.DistributedApplication[0]
Now listening on: https://localhost:17114
info: Aspire.Hosting.DistributedApplication[0]
Login to the dashboard at https://localhost:17114/login?t=6e00479dd713c387209238f98db39b32
info: Aspire.Hosting.DistributedApplication[0]
Distributed application started. Press Ctrl+C to shut down.
We can navigate to the dashboard, and we see that the app shows up:
Last check, click on the link to the app… Hello World!
Thats all I have for today. The process was straightforward, which encourages me to continue investigating Aspire. Next time, I’m going to learn how to deploy the application to Azure. And from there, who know where the path will take me.
As always, you can find the code for this tutorial on my GitHub repo.
Until next time, happy coding!