Read environment variables from web.config in Asp.Net Core

Question

Here my web.config file:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <system.webServer>
    <handlers>
      <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified"/>
    </handlers>
    <aspNetCore processPath="%LAUNCHER_PATH%" arguments="%LAUNCHER_ARGS%" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" forwardWindowsAuthToken="false">
      <environmentVariables>
        <environmentVariable name="TEST_WEBCONFIG_VARIABLE" value="some test webconfig variable value" />
      </environmentVariables>
    </aspNetCore>
  </system.webServer>
</configuration>

How can I read TEST_WEBCONFIG_VARIABLE from my web.config in Startup.cs?

I tried Configuration["TEST_WEBCONFIG_VARIABLE"], but this variable doesn't exist in configuration values list.

Are you running from visual studio?

Sanket
– Sanket

2017-05-11 11:28:12 +00:00
Commented May 11, 2017 at 11:28 — Sanket
– Sanket, Commented May 11, 2017 at 11:28
@Sanket yes, does it matter?

Yurii N.
– Yurii N.

2017-05-11 16:14:23 +00:00
Commented May 11, 2017 at 16:14 — Yurii N.
– Yurii N., Commented May 11, 2017 at 16:14
Yuriy - check my answer below.

Sanket
– Sanket

2017-05-12 16:18:43 +00:00
Commented May 12, 2017 at 16:18 — Sanket
– Sanket, Commented May 12, 2017 at 16:18

Yurii N. · Accepted Answer · 2017-05-15 13:35:13Z

5

While running from Visual Studio, use launchSettings.json like this-

  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development",
        "TEST_WEBCONFIG_VARIABLE":"123"
      }
    },
    "SamplePractice": {
      "commandName": "Project",
      "launchBrowser": true,
      "launchUrl": "http://localhost:5000",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development",
        "TEST_WEBCONFIG_VARIABLE":"123"
      }
    }
  }

Since launchSettings.json is only limited to Visual Studio, In case of publish version use web.config like this-

<aspNetCore processPath="dotnet" arguments=".\MyAspNetCoreApplication.dll" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" forwardWindowsAuthToken="false" >
  <environmentVariables>
    <environmentVariable name="ASPNETCORE_ENVIRONMENT" value="Development" />
    <environmentVariable name="TEST_WEBCONFIG_VARIABLE" value="123" />
  </environmentVariables>
</aspNetCore>

And this environment value will read across application using -

Environment.GetEnvironmentVariable("TEST_WEBCONFIG_VARIABLE");

NOTE! that it only works in case of publish.

edited May 15, 2017 at 13:35

Yurii N.

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answered May 12, 2017 at 16:18

Sanket

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6 Comments

Yurii N. Over a year ago

That's the problem - Environment.GetEnvironmentVariable("TEST_WEBCONFIG_VARIABLE") returns null.

Sanket Over a year ago

Did you added TEST_WEBCONFIG_VARIABLE in launchSettings.json while running from Visual Studio?

Yurii N. Over a year ago

No, do I need it? I thought that TEST_WEBCONFIG_VARIABLE in web.config would be enough.

Sanket Over a year ago

While running from visual studio, env variable pick up from launchsetting.json. in case of publish, it is pick up from web.config.

Yurii N. Over a year ago

Ah, that's explain everything, I'll try to publish it then!

|

Jamadan · Accepted Answer · 2017-05-11 11:04:35Z

3

Pretty sure you just need to call:

For individual setting: Environment.GetEnvironmentVariable("TEST_WEBCONFIG_VARIABLE"‌);

For list of settings: Environment.GetEnvironmentVariables().GetEnumerator();

Because you are accessing EnvironmentVariables from config not AppSettings

answered May 11, 2017 at 11:04

Jamadan

2,3132 gold badges18 silver badges28 bronze badges

2 Comments

Yurii N. Over a year ago

No, it doesn't work, first variant returns null, second - returns all environment variables, but without TEST_WEBCONFIG_VARIABLE.

Jamadan Over a year ago

Hmmmmm. Let me take a quick look into my project

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