Blazor WebAssembly Standalone App targeting .net 9 runs in production mode when started from VS in debug mode

[emil-void]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

I create new Blazor WebAssembly Standalone App template project in Visual Studio 17.12.0 Preview 2.0, targeting .net 9 using the 9.0.100-rc.1.24452.12 version of .net SDK

Then I slightly change the 'Home' page in the 'Pages' folder of the project to display the environment as follows:

@page "/"
@using Microsoft.AspNetCore.Components.WebAssembly.Hosting
@inject IWebAssemblyHostEnvironment Env

<PageTitle>Home</PageTitle>

<h1>Hello, world!</h1>

Welcome to your new app.

<p>Environment: @Env.Environment</p>

Now, when I run the project in VS debug mode, I get this result

indicating, that the project runs as in production environment (not correct IMO), even though the generated launchSettings.json sets the 'ASPNETCORE_ENVIRONMENT' as 'Development'

"https": {
  "commandName": "Project",
  "dotnetRunMessages": true,
  "launchBrowser": true,
  "inspectUri": "{wsProtocol}://{url.hostname}:{url.port}/_framework/debug/ws-proxy?browser={browserInspectUri}",
  "applicationUrl": "https://localhost:7299;http://localhost:5176",
  "environmentVariables": {
    "ASPNETCORE_ENVIRONMENT": "Development"
  }
}

When I follow the exact steps in the same Visual Studio using the same .net SDK version with the only difference - targeting .net 8 (instead of .net 9) I get this:

The environment is 'Development' which I tend to consider as correct behavior

Expected Behavior

Running Blazor WebAssembly Standalone App project from VS in 'debug' mode with

"ASPNETCORE_ENVIRONMENT": "Development"

set in launchSettings.json

should set the environment to 'Development' instead to 'Production'

Steps To Reproduce

No response

Exceptions (if any)

No response

.NET Version

9.0.100-rc.1.24452.12

Anything else?

.NET SDK:
Version: 9.0.100-rc.1.24452.12
Commit: 81a714c6d3
Workload version: 9.0.100-manifests.67cd1eb6
MSBuild version: 17.12.0-preview-24422-09+d17ec720d

Runtime Environment:
OS Name: Windows
OS Version: 10.0.22631
OS Platform: Windows
RID: win-x64