Environment.GetEnvironmentVariable won't find variable value

Why won't Environment.GetEnvironmentVariable("variableName") get a variable's value if the call is made from within a webMethod hosted on IIS and it will work if I call it from a console application on the same machine?

Where do I set up those variables to be visible to IIS web services? Should I use the second parameter from Environment.GetEnvironmentVariable(name, target) to get it?

It is actually really simple:

[WebMethod(Description = "Gets the environment variable value.")]
public string GetEnvironmentVariable()
{
    return Environment.GetEnvironmentVariable("VARIABLE_NAME_HERE");
}

And by the way, VARIABLE_NAME_HERE is set at the system and user level.

Restarting Visual Studio fixed it for me (guessing IIS Express also caches these values).

I faced the same issue, and thanks to sergserg's answer, I came up with this and it worked:

var value = Environment.GetEnvironmentVariable(key, EnvironmentVariableTarget.User)

The important bit was using EnvironmentVariableTarget.User

Read here for more information:

Using System Wide Environment Variables in .NET Application

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Specifically:

> What Are System Environment Variables? > > Environment variables are strings that save information about the > entire environment in your system. These string values are dynamic and > they can affect the way your system will behave on. Environment > variables can be classified into two main types: > > System Variables: They affect the entire system whatever the current > user is. They are defined by Windows and saved in the registry. You > need to be an administrator to be able to modify them. You usually > need to restart your computer to make these changes effective. > > User Variables: They affect the current environment of the current > system user. They can be deleted, modified, and added by any system > user. They are used by Windows setup, by some programs, and by users. > Changes to these variables are saved to the registry and be effective > immediately.

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If you try to access an environment variable that does not exist on your machine you will have issues. You must be trying to find a variable that exists on your local machine, but not on your web service's host machine.

You need to restart IIS by using the iisreset command.

There's a DLL or some code snipped that is shared by cmd, PowerShell, and Visual Studio (maybe also by VS Code) that caches environment variables (separately for each app) when they load.

So, if you are testing something for which you're changing environment variables, instead of restarting your IDE (which is slow), you can just start a separate cmd or PowerShell to test, change environment variables, and then just restart that cmd or PowerShell. I recommend PowerShell because you can use the up arrow to reuse commands typed in previous sessions.

My project's csproj file did not have (or expected) the local.settings.json. By adding it's update node, the Environment.GetEnvironmentVariable("variablename") started working and fetching the information from variables.

<ItemGroup>
    <None Update="host.json">
        <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
        <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
        <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
</ItemGroup>