How Do You Access the `applicationUrl` Property Found in launchSettings.json from Asp.NET Core 3.1 Startup class?

Question

I am currently creating an Asp.NET Core 3.1 API Application. In it, I have a launchSettings.json that looks like the following:

{
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:61392",
      "sslPort": 44308
    }
  },
  "$schema": "http://json.schemastore.org/launchsettings.json",
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "launchUrl": "weatherforecast",
      "environmentVariables": {
        "Key": "Value",
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "Application.API": {
      "commandName": "Project",
      "launchBrowser": true,
      "launchUrl": "weatherforecast",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      },
      "applicationUrl": "https://localhost:5001;http://localhost:5000"
    }
  }
}

In particular, I am interested in obtaining the applicationUrl values defined in this file. Unfortunately, I do not see any obvious way to access them outside of loading the file directly via JSON serialization and probing the values there.

As such, I am looking for a more elegant solution. Is there a way to access these values from within the Startup.Configure and/or Startup.ConfigureServices methods?

I am thinking of something like:

public void Configure(IApplicationBuilder builder)
{
    var url = builder.ApplicationServices.GetRequiredService<IServerHostingEnvironment>().ApplicationUrl
}

For reference, I did see this question, but it seems that this requires an HTTP request. In my case, I am still configuring the server before a request has been made.

For further reference and context: I am building a .NET GitHub App application, and am making the corresponding equivalent of the Smee.io client, whose Javascript code can be found here.

The client takes a source (via Server-sent events) and sends it to a target. I got the source figured out and configured, but am ironically having trouble accessing and establishing the target URL (the applicationUrl seen above) in an obvious and configured fashion.

Finally, I realize I could hardcode the value in appSettings.json, but that would then mean I would be maintaining the same value in two places -- one in appSettings.json and one in the already-existing launchSettings.json. I would rather keep it to one place to reduce maintenance burden, if possible.

Answer 1

I was actually looking for something similar myself recently.

It turns out you can determine what URL's were passed to the application by Visual Studio during a debugging session (from applicationUrl within launchSettings.json) By looking at the environmental variables.

Although bearing in mind this is probably only useful for debugging within VStudio IDE which uses the launchSettings.json file

var urls = Environment.GetEnvironmentVariable("ASPNETCORE_URLS").Split(";");

Answer 2

Have not tested it but I use this pattern to access appsettings.json.

In startup.cs add launchsettings.json to the configuration builder:

public Startup(IConfiguration configuration)
    {
        var builder = new ConfigurationBuilder().AddJsonFile(Path.Combine(Directory.GetCurrentDirectory(), "Properties", "launchSettings.json"));
        Configuration = builder.Build();
    }

public IConfiguration Configuration { get; }

Add it as a service:

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton <IConfiguration> (Configuration);
}

Inject it in controller and get key value:

public class SomeController: ControllerBase {  
    private IConfiguration _iconfiguration;  
    public SomeController(IConfiguration iconfiguration) {  
        _iconfiguration = iconfiguration;  
    }
void SomeMethod(){
string appUrl = _iConfiguration.GetValue<string>("applicationUrl","someDefaultValue")

} }
Hope this helps you out!