Aspnet core 5.0 inject dependency in startup.cs constructor

Question

I'm trying to add a parameter to the constructor of the Startup class in Asp.net core using this method: https://mattmazzola.medium.com/asp-net-core-injecting-custom-data-classes-into-startup-classs-constructor-and-configure-method-7cc146f00afb

However, this doesn't work for me. Here's my C# Code:

public class AppAProgram
{
    #region Members
    private IHostBuilder hostBuilder;

    private IHost host;
    #endregion

    #region Constructors
    public AppAProgram(string[] args)
    {
        this.hostBuilder = Host.CreateDefaultBuilder(args);
        ILauncherContext launcherContext = new DummyLauncherContext();
        this.hostBuilder.ConfigureServices((hostContext, services) => { services.AddSingleton<ILauncherContext>(launcherContext); });
        this.hostBuilder.ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<AppAStartup>(); });
        this.host = hostBuilder.Build();
    }
    #endregion

    public static void Main(string[] args)
    {
        AppAProgram appAProgram = new AppAProgram(args);    
        appAProgram.Start();
    }

    public void Start()
    {
        this.host.Run();
    }
}

Here's the constructor for which I add an injected parameter:

    #region Constructors
    public AppAStartup(IConfiguration configuration, ILauncherContext launcherContext)
    {
        Configuration = configuration;
        this.launcherContext = launcherContext;
    }
    #endregion

When I do this, I get this exception:

System.InvalidOperationException: 'Unable to resolve service for type 'Spike.Run.Launcher.ILauncherContext' while attempting to activate 'Spike.Run.AppA.AppAStartup'.'

while injecting dependencies into the Startup's constructor is something funny to play, do you have an actual reason why you want that? Any possible scenarios for that? — King King, Jan 14 '21 at 20:37
Shouldn't you use `services.AddSingleton()` to add the dependency? Instead of creating the object yourself. — JHBonarius, Jan 14 '21 at 20:39

Nkosi · Accepted Answer · 2021-01-14T20:18:50.343

Reference The Startup class

Only the following service types can be injected into the Startup constructor when using the Generic Host (IHostBuilder):

IWebHostEnvironment

IHostEnvironment

IConfiguration

...

Most services are not available until the Configure method is called.

emphasis mine

Use the Configure method instead

public AppAStartup(IConfiguration configuration) {
    Configuration = configuration;        
}

public void Configure(IApplicationBuilder app, ..., ILauncherContext launcherContext) {

    //access launcherContext here

    //...
}

Aspnet core 5.0 inject dependency in startup.cs constructor

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