Using complex structures with AddEnvironmentVariables - .net-core

Question

Question
How to handle complex structures, such as arrays, when using the ConfigurationBuilder's AddEnvironmentVariables approach for setting config.
i.e. What would the environment variables be called to represent the below structure?
{
"MyApp": {
"SendAlertsTo": [
{"Name": "Joe Blogger", "Email": "JoeBlogger#example.com"},
{"Name": "Jane Doer", "Email": "JaneDoer#example.com"}
]
}
}
Detailed version with context
We're writing apps that will be hosted in containers. Initially we'd continued to use the AppSettings.json file to hold settings, populating this file's contents from environment variables at startup via an entrypoint.sh shell script.
We later realised that we could use the ConfigurationBuilder's AddEnvironmentVariables method to pull the values directly from the environment variables, and thus avoid the overhead of maintaining the entrypoint.sh script as being another place to update each time a new setting was added.
This works well for an app settings file such as:
{
"MyApp": {
"SmtpServer": "smtp.example.com",
"FromAddress": "JoeyBlogger#example.com"
},
"Logging": {
"LogLevel": "Default"
}
}
.. as this translates simply to:
export MyApp:SmtpServer=smtp.example.com
export MyApp:FromAddress=JoeyBlogger#example.com
export Logging:LogLevel=Default
However, I recently saw a developer's app settings file for some new monitoring, which looks like the below (note; this won't be the actual settings used in our hosted environments; it's just an example which triggered this question). In this case, using the above approach doesn't work so well, since there would be two different settings with the name Serilog:WriteTo:Name, and ambiguity over which entry anything starting Serilog:WriteTo:Args:* relates to.
{
"Serilog"
"WriteTo": [
{
"Name": "Async",
"Args": {
"configure": [
{
"Name": "File",
"Args": {
"path": ".\\log.txt",
"rollingInterval": "Day",
"retainedFileCountLimit": 7,
"buffered": true
}
}
]
}
},
{
"Name": "Async",
"Args": {
"configure": [
{
"Name": "Console"
}
]
}
}
]
}
}
My guess is we'd handle this via some sort of index; but I've not been able to find anything in the docs about this.
export Serilog:WriteTo[0]:Name=Async
export Serilog:WriteTo[0]:Args:configure[0]:Name=File
export Serilog:WriteTo[0]:Args:configure[0]:Args:path=.\\log.txt
export Serilog:WriteTo[0]:Args:configure[0]:Args:rollingInterval=Day
export Serilog:WriteTo[0]:Args:configure[0]:Args:retainedFileCountLimit=7
export Serilog:WriteTo[0]:Args:configure[0]:Args:buffered=true
export Serilog:WriteTo[1]:Name=Async
export Serilog:WriteTo[1]:Args:configure[0]:Name=Console
However, running a quick PoC shows that the above doesn't work. How can this be done?

Answer 1

I found the solution here: MS Extensions Configuration Deep Dive.
The answer is that indexes are used, but the index number is treated like a named element; i.e.
{
"MyApp": {
"SendAlertsTo": [
{"Name": "Joe Blogger", "Email": "JoeBlogger#example.com"},
{"Name": "Jane Doer", "Email": "JaneDoer#example.com"}
]
}
}
Becomes:
export MyApp:SendAlertsTo:0:Name=Joe Blogger
export MyApp:SendAlertsTo:0:Email=JoeBlogger#example.com
export MyApp:SendAlertsTo:1:Name=Jane Doer
export MyApp:SendAlertsTo:1:Email=JaneDoer#example.com
Additionally, for Linux hosting there's another point I'd not been aware of / unrelated to the array question.. the : separator should be __, so the above becomes:
export MyApp__SendAlertsTo__0__Name=Joe Blogger
export MyApp__SendAlertsTo__0__Email=JoeBlogger#example.com
export MyApp__SendAlertsTo__1__Name=Jane Doer
export MyApp__SendAlertsTo__1__Email=JaneDoer#example.com