Is ConfigurationManager.AppSettings available in .NET Core 2.0?

I've got a method that reads settings from my config file like this:

var value = ConfigurationManager.AppSettings[key];

It compiles fine when targeting .NET Standard 2.0 only.

Now I need multiple targets, so I updated my project file with:

<TargetFrameworks>netcoreapp2.0;net461;netstandard2.0</TargetFrameworks>

But now, the compilation fails for netcoreapp2.0 with the following error message:

Error CS0103 The name 'ConfigurationManager' does not exist in the current context (netcoreapp2.0)

Separately, I created a new .NET Core 2.0 console application (only targeting .NET Core 2.0 this time), but likewise there seems to be no ConfigurationManager under the namespace System.Configuration.

I'm quite confused because it's available under .NET Standard 2.0, so I would expect it to be available in .NET Core 2.0, as .NET Core 2.0 is .NET Standard 2.0 compliant.

What am I missing?

Yes, ConfigurationManager.AppSettings is available in .NET Core 2.0 after referencing NuGet package System.Configuration.ConfigurationManager.

Credits goes to @JeroenMostert for giving me the solution.

I installed System.Configuration.ConfigurationManager from Nuget into my .net core 2.2 application.

I then reference using System.Configuration;

Next, I changed

WebConfigurationManager.AppSettings

to ..

ConfigurationManager.AppSettings

So far I believe this is correct. 4.5.0 is typical with .net core 2.2

I have not had any issues with this.

Once you have the packages setup, you'll need to create either an app.config or web.config and add something like the following:

<configuration>
  <appSettings>
    <add key="key" value="value"/>
  </appSettings>
</configuration>

The latest set of guidance is as follows: (from https://docs.microsoft.com/en-us/azure/azure-functions/functions-dotnet-class-library#environment-variables)

Use:

System.Environment.GetEnvironmentVariable(name, EnvironmentVariableTarget.Process);

From the docs:

public static class EnvironmentVariablesExample
{
    [FunctionName("GetEnvironmentVariables")]
    public static void Run([TimerTrigger("0 */5 * * * *")]TimerInfo myTimer, ILogger log)
    {
        log.LogInformation($"C# Timer trigger function executed at: {DateTime.Now}");
        log.LogInformation(GetEnvironmentVariable("AzureWebJobsStorage"));
        log.LogInformation(GetEnvironmentVariable("WEBSITE_SITE_NAME"));
    }

    public static string GetEnvironmentVariable(string name)
    {
        return name + ": " +
            System.Environment.GetEnvironmentVariable(name, EnvironmentVariableTarget.Process);
    }
}

App settings can be read from environment variables both when developing locally and when running in Azure. When developing locally, app settings come from the Values collection in the local.settings.json file. In both environments, local and Azure, GetEnvironmentVariable("<app setting name>") retrieves the value of the named app setting. For instance, when you're running locally, "My Site Name" would be returned if your local.settings.json file contains { "Values": { "WEBSITE_SITE_NAME": "My Site Name" } }.

The System.Configuration.ConfigurationManager.AppSettings property is an alternative API for getting app setting values, but we recommend that you use GetEnvironmentVariable as shown here.