In dotnet we now have the ability to build a container using only the dotnet cli without the need for a Dockerfile. This capability is used in the Aspire project https://learn.microsoft.com/en-us/dotnet/aspire/ from Microsoft, which is an opinionated, cloud ready stack for building distributed applications. In this article we will just look at building and running a container for a web project and a console application.
dotnet new mvc --output container-app-web --name container-app-web
cd container-app-web
dotnet run$ dotnet run
Building...
info: Microsoft.Hosting.Lifetime[14]
Now listening on: [http://localhost:5108](http://localhost:5108/)
info: Microsoft.Hosting.Lifetime[0]
Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
Content root path: /home/me/repositories/dotnet/container-app-web
warn: Microsoft.AspNetCore.HttpsPolicy.HttpsRedirectionMiddleware[3]
Failed to determine the https port for redirect.
Visit the url logged in the console http://localhost:5108 to check it works
dotnet publish --os linux --arch x64 /t:PublishContainer -c Release$ dotnet publish --os linux --arch x64 /t:PublishContainer -c Release
MSBuild version 17.8.5+b5265ef37 for .NET
Determining projects to restore...
Restored /home/me/repositories/dotnet/container-app-web/container-app-web.csproj (in 219 ms).
container-app-web -> /home/me/repositories/dotnet/container-app-web/bin/Release/net8.0/linux-x64/container-app-web.dll
container-app-web -> /home/me/repositories/dotnet/container-app-web/bin/Release/net8.0/linux-x64/publish/
Building image 'container-app-web' with tags 'latest' on top of base image '[mcr.microsoft.com/dotnet/aspnet:8.0](http://mcr.microsoft.com/dotnet/aspnet:8.0)'.
Pushed image 'container-app-web:latest' to local registry via 'docker'.Run it with docker.
docker run -p 8080:8080 container-app-web:latest$ docker run -p 8080:8080 container-app-web:latest
warn: Microsoft.AspNetCore.DataProtection.Repositories.FileSystemXmlRepository[60]
Storing keys in a directory '/home/app/.aspnet/DataProtection-Keys' that may not be persisted outside of the container. Protected data will be unavailable when container is destroyed. For more information go to [https://aka.ms/aspnet/dataprotectionwarning](https://aka.ms/aspnet/dataprotectionwarning)
warn: Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[35]
No XML encryptor configured. Key {2b48b911-d884-40e2-82ff-7e2a94e3a80b} may be persisted to storage in unencrypted form.
info: Microsoft.Hosting.Lifetime[14]
Now listening on: http://[::]:8080
info: Microsoft.Hosting.Lifetime[0]
Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
Hosting environment: Production
info: Microsoft.Hosting.Lifetime[0]
Content root path: /appVisit http://localhost:8080 to try out the web app container
To do the same thing for a console app we need to add the Microsoft.NET.Build.Containers package to the console project.
https://github.com/dotnet/sdk-container-builds/blob/main/docs/GettingStarted.md#build-a-container
dotnet new console --output container-console --name container-console
cd container-console
dotnet add package Microsoft.NET.Build.Containers
dotnet runThere is a bit of discussion around needing to pass the command line switches differently for web and console apps but using the same command worked fine for me
dotnet publish --os linux --arch x64 /t:PublishContainer -c Release$ dotnet publish --os linux --arch x64 /t:PublishContainer -c Release
MSBuild version 17.8.5+b5265ef37 for .NET
Determining projects to restore...
Restored /home/me/repositories/dotnet/container-console/container-console.csproj (in 484 ms).
container-console -> /home/me/repositories/dotnet/container-console/bin/Release/net8.0/linux-x64/container-console.dll
/home/me/.nuget/packages/microsoft.net.build.containers/8.0.204/build/Microsoft.NET.Build.Containers.targets(194,5): warning : Microsoft.NET.Build.Containers NuGet package is explicitly referenced. Consider removing the package reference to Microsoft.NET.Build.Containers as it is now part of .NET SDK. [/home/neil/repositories/dotnet/container-console/container-console.csproj]
container-console -> /home/me/repositories/dotnet/container-console/bin/Release/net8.0/linux-x64/publish/
Building image 'container-console' with tags 'latest' on top of base image '[mcr.microsoft.com/dotnet/runtime:8.0](http://mcr.microsoft.com/dotnet/runtime:8.0)'.
Pushed image 'container-console:latest' to local registry via 'docker'.As you can see from the log output this publishes an image called container-console:latest which we can then run.
docker run container-console:latestAnd below shows the result.
$ docker run container-console:latest
Hello, World!
$It is great that we have this capability without needing to learn how to write Dockerfiles. We also have ways to customise the container using the project file, as described here https://github.com/dotnet/sdk-container-builds/blob/main/docs/ContainerCustomization.md