Explanation:

Box 1: microsoft.com/dotnet/sdk:2.3
The first group of lines declares from which base image we will use to build our container on top of. If the local system does not have this image already, then docker will automatically try and fetch it. The mcr.
microsoft.com/dotnet/core/sdk:2.1 comes packaged with the .NET core 2.1 SDK installed, so it ' s up to the task of building ASP .NET core projects targeting version 2.1 Box 2: dotnet restore The next instruction changes the working directory in our container to be /app, so all commands following this one execute under this context.
COPY *.csproj ./
RUN dotnet restore
Box 3: microsoft.com/dotnet/2.2-aspnetcore-runtime
When building container images, it ' s good practice to include only the production payload and its dependencies in the container image. We don ' t want the .NET core SDK included in our final image because we only need the .NET core runtime, so the dockerfile is written to use a temporary container that is packaged with the SDK called build-env to build the app.
Reference:
https://docs.microsoft.com/de-DE/virtualization/windowscontainers /quick-start/building-sample-app

https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions
" We strongly recommend that you include the version of the action you are using by specifying a Git ref, SHA, or Docker tag. If you don ' t specify a version, it could break your workflows or cause unexpected behavior when the action owner publishes an update. Using the commit SHA of a released action version is the safest for stability and security. If the action publishes major version tags, you should expect to receive critical fixes and security patches while still retaining compatibility. Note that this behavior is at the discretion of the action ' s author. Using the default branch of an action may be convenient, but if someone releases a new major version with a breaking change, your workflow could break. "

Explanation:

Box 1: Progressive exposure
Continuous Delivery may sequence multiple deployment "rings" for progressive exposure (also known as
"controlling the blast radius"). Progressive exposure groups users who get to try new releases to monitor their experience in "rings." The first deployment ring is often a "canary" used to test new versions in production before a broader rollout. CD automates deployment from one ring to the next and may optionally depend on an approval step, in which a decision maker signs off on the changes electronically. CD may create an auditable record of the approval in order to satisfy regulatory procedures or other control objectives.

Box 2: Feature flags
Feature flags support a customer-first DevOps mindset, to enable (expose) and disable (hide) features in a solution, even before they are complete and ready for release.
Box 3: Blue/green
Blue/green deployments which means that instead of replacing the previous version (here we refer to this version as blue), we bring up the new version (here referred to as the green version) next to the existing version, but not expose it to the actual users right away. On the condition of having successfully validated that the green version works correctly, we will promote this version to the public version by changing the routing configuration without downtime. If something is wrong with the green version we can revert back without users every noticing interruptions.
Reference:
https://docs.microsoft. com/en-us/azure/devops/learn/what-is-continuous-delivery
http s://docs.microsoft.com/en -us/azure/devops/mi grat e/phase- feature s-w ith-featur e-flags
https://medium.com/@denniszielke/continuous-kubernetes -blue-green-deployments-on -azure-using-nginx -appgateway-or-trafficmanager-4490bce29cb

To start monitoring all pipelines in a project, use the following command inside a channel:
@azure pipelines subscribe [project url]
The project URL can be to any page within your project (except URLs to pipelines).
For example:
@azure pipelines subscribe https://dev.azure.com/myorg/myproject/
Reference:
https ://docs.microsoft.com/en- us/azure/devops/pipeline s/integrations/microsoft-teams