What

This project demonstrates Microsoft's chained configuration behavior for .NET generic host apps.

Uses NET 6.0 and the generic host builder in a console app, with a "Greeting" property that is overridden with each chain in the configuration.

Behavior

This is the order in which each chained configuration provider is applied. Last one wins.

1. Environment variable
2. AppSettings.json
3. AppSettings.{{DOTNET_ENVIRONMENT}}.json
4. Command-line argument
5. LaunchSettings.json (if DOTNET_ENVIRONMENT is "Development" and running from Visual Studio)
6. Azure App Configuration

Why

Sometimes understanding the chained configuration and what overrides what can be a bigger learning curve than desired.

This demo is to help with your understanding of the order of the chained configuration.

How

Instructions

1. Clone this Gitlab project to your local
2. Bring up to Visual Studio
3. Follow the use cases, below
4. Explore to your heart's content

Prerequisites

1. 1. A CLi of your choice (see more below)
2. Azure subscription (optional, see details below)
3. Visual Studio

Azure App Config

The Azure configuration part of this demo uses Azure App Configuration access, which is currently free for one resource.

If using this part of the demo, you must setup your Azure subscription and environment prior to launching the demo.

I used the "Greeting" configurable property, one with a label, one without. If you want to use these, or just one or the other, you will need to add them to your Azure App Config.

The labeled one must match "chained-configuration" per the existing code.

You must also uncomment the AddAzureAppConfiguration section in Program.cs.

Command-Line

Familiarity with a command-line is required. Examples are based on Git Bash for Windows, but can easily be mapped for Powershell or CMD.

Use Cases

These assume a bash terminal. Convert to commands for your favorite terminal/Powershell/CMD window.

These work backwards from Azure App Config, that overrides all previous settings, to the lowest priority in the chain.

When running from the command-line, clean (with no environment variables set):

6. Azure App Config Trumps All

With the AzureAppConfiguration section of Program.cs uncommented,

~/source/repos/ChainedConfigurationDemo/pub  master
└─➤ cd ..; dotnet publish -o pub --nologo --verbosity quiet; cd pub

~/source/repos/ChainedConfigurationDemo/pub  master
└─➤ ./ChainedConfigurationDemo.exe Greeting=HelloFromArgs
Starting demo...

In the end, the greeting is "HelloFromAzure"

Press Ctrl-C to stop the host and exit.

5. LaunchSettings.Json

With the AzureAppConfiguration section of Program.cs commented, inside Visual Studio, run the app in Debug.

4. Command-Line Argument

With Azure commented out, and no DOTNET_ENVIRONMENT set, not launching from Visual Studio's launchSettings,

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ cd ..; dotnet publish -o pub --nologo --verbosity quiet; cd pub

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ ./ChainedConfigurationDemo.exe Greeting=HelloFromArgs
Starting demo...

In the end, the greeting is "HelloFromArgs"

Press Ctrl-C to stop the host and exit.

3. AppSettings.{{DOTNET_ENVIRONMENT}}.json

This app is configured such that if the DOTNET_ENVIRONMENT is not set, or is set to something other than "Development" or "Test", the configuration building falls through to appsettings.json (if the property exists in appsettings.json), and so on -- like, for example, if DOTNET_ENVIRONMENT is set to "Production".

3a. AppSettings.Development.json

• With the AzureAppConfiguration section of Program.cs commented
• With no arguments
• With DOTNET_ENVIRONMENT set
• From the command line (launchSettings not used)

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ cd ..; dotnet publish -o pub --nologo --verbosity quiet; cd pub

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ export DOTNET_ENVIRONMENT=Development

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ ./ChainedConfigurationDemo.exe
Starting demo...

In the end, the greeting is "HelloFromAppSettings.Development"

Press Ctrl-C to stop the host and exit.

3b. AppSettings.Test.json

• With the AzureAppConfiguration section of Program.cs commented
• With no arguments
• With DOTNET_ENVIRONMENT set
• From the command line (launchSettings not used)

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ cd ..; dotnet publish -o pub --nologo --verbosity quiet; cd pub

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ export DOTNET_ENVIRONMENT=Test

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ ./ChainedConfigurationDemo.exe
Starting demo...

In the end, the greeting is "HelloFromAppSettings.Test"

Press Ctrl-C to stop the host and exit.

2. AppSettings.json

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ unset DOTNET_ENVIRONMENT

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ ./ChainedConfigurationDemo.exe
Starting demo...

In the end, the greeting is "HelloFromAppSettings"

Press Ctrl-C to stop the host and exit.

With the app's current configuration, this is the same result as in production.

4. Environment Variable

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ export Greeting=HelloFromOperatingEnvironment

 ~/source/repos/ChainedConfigurationDemo/pub  master
 └─➤ ./ChainedConfigurationDemo.exe
Starting demo...

In the end, the greeting is "HelloFromOperatingEnvironment"

Press Ctrl-C to stop the host and exit.

(make sure to unset Greeting if in the cli environment for all other cases)

Configuration

For the optional Azure use case, you will need

1. To uncomment the Azure section in Program.cs
2. Your own Azure subscription
3. An Azure App Configuration property called "Greeting"
4. A way for your local box to access the Azure App Config property

For #4, this demo uses the read-only connection string from my Azure App Config, pulled in as an environment variable from my local system.