Reference a service in object construction before the service is built. C#

builder.Services.AddSingleton<RunningGameService>(); 

builder.Services.AddAuthorization(options =>
{
    options.AddPolicy("GameGroupsAuthorisationConnect", policy =>
    {
        policy.Requirements.Add(new GameGroupsAuthorisationConnectRequirement());
    });
});

Hi,
The problem I have is that the GameGroupsAuthorisationConnectRequirement is dependent on RunningGameService, and hence it requires a reference to it in the constructor.

I'm a tad lost with this.
Thanks in advance.

A requirement should not depend on a service; it just defines the parameters that are applicable for the authorization.

From the documentation

> An authorization requirement is a collection of data parameters that a policy can use to evaluate the current user principal.

For example

public class GameGroupsAuthorisationConnectRequirement : IAuthorizationRequirement
{ 
    // Any properties in case applicable.
}

It is the accompanying AuthorizationHandler that deals with the requirement that can have services injected.

public class GameGroupsAuthorisationConnectRequirementHandler  
    : AuthorizationHandler<GameGroupsAuthorisationConnectRequirement>
{
    public GameGroupsAuthorisationConnectRequirementHandler(
        RunningGameService runningGameService
        /* Inject other services here */ 
        )
    { 
        // ...
    } 

    protected override Task HandleRequirementAsync(
        AuthorizationHandlerContext context, GameGroupsAuthorisationConnectRequirement requirement
        )
    {
        // ...
        
        context.Succeed(requirement);
        
        return Task.CompletedTask;
    }
}

That handler gets registered as below. Doing so it gets its services resolved from the DI container.

builder.Services.AddSingleton<IAuthorizationHandler, GameGroupsAuthorisationConnectRequirementHandler>();

See Dependency injection in requirement handlers in ASP.NET Core.

The way you defined your policy can stay as-is.

options.AddPolicy("GameGroupsAuthorisationConnect", policy =>
{
    policy.Requirements.Add(new GameGroupsAuthorisationConnectRequirement());
});

Use an overload of AddSingleton that accepts an instance instead of a generic parameter, like this:

// Obviously you need to satisfy _this_ service's required constructor params here...
var rgService = new RunningGameService(...); 
builder.Services.AddSingleton<RunningGameService>(rgService); 

builder.Services.AddAuthorization(options =>
{
    options.AddPolicy("GameGroupsAuthorisationConnect", policy =>
    {
        policy.Requirements.Add(new GameGroupsAuthorisationConnectRequirement(rgService));
    });
});