Setting the Staging & Production Environments During Development

In our previous post, we examined the flexibility provided by the .NET configuration infrastructure.

In this case, we will tackle a common problem - you want to see how your application will behave in different environments while it is still under development. In other words, you want to simulate other environments.

Remember, by default, if you don’t do anything, dotnet run sets the environment to Development.

If you want to change it, pass the command like parameter --Environment and set the value you want. The parameter, at least for macOS, is case sensitive - you must specify --Environment as shown.

The documentation (at last as of today 11 May 2025) is incorrect as it says --environment.

So if we have an options file appsettings.Staging.json that looks like this:

{
  "SystemSettings": {
    "ForegroundColour": "Cyan",
    "BackgroundColour": "FireRed"
  }
}

If we run our app like this:

dotnet run --Environment Staging

We should see the appropriate environment printed:

We need to make one more change for everything to work.

Custom json files always override those loaded by the system, one of which is appsettings.Staging.json.

To avoid the developer settings being a consideration for Staging and Production, we can update our code to only load developer settings if the environment is Development.

// Check if we are running in development
if (builder.Environment.IsDevelopment())
{
    // Load optional developer-specific settings
    builder.Configuration.AddJsonFile($"appsettings.{Environment.MachineName}.json", optional: true);
}

If we run our endpoint we should now see the correct results.

TLDR

You can set the environment an application is running under by passing the command line environment --Environment

The code is in my GitHub.

Happy hacking!