How and where to define an environment variable on Azure

I have an ASP.NET MVC web application deployed to Azure. I'm reading my setting using the GetEnvironmentVariable(...) method.

The problem is that I can't find a way to define this environment variable in Azure Portal. Where can I do that?

I don't want to have this stuff in a file. Data that will be there are credentials.

I assume you are using Azure App Service (formerly known as Azure Websites).

To define your own environment variable, click to your site → All Settings → Application settings:

Add an app setting in the "App settings" section:

You can verify the value from the debug console.

Going to https://{your site name}.scm.azurewebsites.net/DebugConsole:

I came across this question when facing the same problem myself. Well, just to give a clearer answer which I found at blog.elmah.io.

All you need to do is:

1. Include the new appsetting.{env}.json in the publishOptions in file project.json.
2. Go to Azure Portal and open the web application.
3. Select application settings.
4. Add an entry for ASPNETCORE_ENVIRONMENT and set it to whatever you want.

That's it.

In the new version 2021 go to the resource -> Configuration.

Then click on "New application settings".

Then add "ASPNETCORE_ENVIRONMENT" as key and click on OK then Save.

Note that you must have the appsettings.(environment).json file for .Net Core.

I know OP specified in the portal, but command line is more repeatable. To do it using Azure CLI:

az webapp config appsettings set -n $webappname -g $resourceGroupName --settings ConnectionStrings__Default=$connectionString

To set an environment variable ConnectionStrings__Default to the variable $connectionString

(2019 version) Navigate to your AppService in the Azure cloud portal then Configuration.

Actually this solves my problem (which I found yesterday - and it's on Scott Hanselman's blog also):

Best practices for private config data and connection strings in configuration in ASP.NET and Azure

TLDR;

Put settings in a separate file that doesn't go to the repository and are not being deployed to the server. Next define missing variables in app settings like Xiaomin Wu showed.

In these modern times, when publishing from Visual Studio 2019, on the publish page there is a link called "Manage Azure App Service settings". In there you can create and define environment variables that get set when you publish. Very easy if you know where to look!