Override ASP.NET Nested Configuration Using Environment Variable

Question

If a configuration file has a nested structure in it, what naming convention or variable name format is used to override that value in a command line environment like Powershell?

.NET config.json file:

{
    "L1a": {
        "L1a2a": {
            "L1a2a1": "value"
        },
        "L2b": false
    },
    "L1b": false
}

From the .NET application code, the configuration values can be accessed like this:

configObject["L1a:L1a2a:L1a2a1"];
configObject["L1a:L2b"];
configObject["L1b"];

Overriding a top level value using an environment variable is easy - just use the same key name:

$env:L1b = "true"

How can I set environment variables in Powershell to override the nested configuration file values?

L1a:L1a2a:L1a2a1 and L1a-L2b are not valid environment variable names. Using underscore like L1a_L2b does not work.

I think the answer might require using a hash table or dictionary object like @{ key = value }, but I can't get that to work either. — ulty4life
– ulty4life, Commented Aug 5, 2015 at 18:16
It's still not clear to me how this all is related. You have a .NET application that reads a JSON config file. Where exactly do PowerShell and environment variables come into play here? Does the application expose the configuration as environment variables? — Ansgar Wiechers
– Ansgar Wiechers, Commented Aug 5, 2015 at 18:44
@AnsgarWiechers it all has to do with the ASP.NET 5 configuration framework. docs.asp.net/en/latest/fundamentals/configuration.html — ulty4life
– ulty4life, Commented Aug 5, 2015 at 18:49

Kraego · Accepted Answer · 2022-04-12 16:34:17Z

7

You should use __ as seperator for your environment variable hierarchie see aspnetcore-6.0#environment-variables because it is platform agnostic (also applies to .net 5). This is the platform agnostic way of asp .net (will work in docker, linux and linux ...)

${env__L1a__L1a2a__L1a2a1} = 'othervalue'

edited Apr 12, 2022 at 16:34

answered Apr 12, 2022 at 11:22

Kraego

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1 Comment

Levi Fuller Over a year ago

Definitely use __ to avoid platform-specific issues

Ansgar Wiechers · Accepted Answer · 2015-08-05 18:59:09Z

2

You can define/access environment variables with colons (or other special characters) in their names by enclosing the variable name in curly brackets:

${env:L1a:L1a2a:L1a2a1} = 'othervalue'

edited Aug 5, 2015 at 18:59

answered Aug 5, 2015 at 18:33

Ansgar Wiechers

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3 Comments

ulty4life Over a year ago

I'm asking specifically about overriding ASP.NET 5 configuration settings. I either don't understand your answer, or think you've missed the point.

ulty4life Over a year ago

I just tried the curly braces to escape the variable name, and that worked. Thanks! The rest of the answer isn't really relevant. Sorry for the confusion around ASP.NET 5.

oshan2csd Over a year ago

How do you save nested config data into an environment variable? I have '__' but didn't worked

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