Can I create instance of plain c# class via VContainer without registering it?

[Severskiys]

For monobehaviour i can use - container.InjectGameObject(gameObject). But if i need plain c# class instance: i register it first (builder.Register()), then resolve (await container and var instance = container.Resolve()).

Can i get similar result with only one operation? For situations when i definitely do not need that instance as dependency for any other class.

[tigran-sargsyan-w]

Resolve() itself expects T to already be registered in the container, so there isn't a built-in Resolve() mode that automatically treats every unknown concrete type as transient.

However, if what you want is simply:

"construct this concrete C# type once and let VContainer resolve/inject its dependencies"

you can build a transient registration on the fly and resolve that registration directly:

public static T Create<T>(this IObjectResolver resolver)
{
    var registration =
        new RegistrationBuilder(typeof(T), Lifetime.Transient)
            .Build();

    return (T)resolver.Resolve(registration);
}

Then:
var instance = container.Create<MyClass>();
MyClass itself does not need to be added to the container registry, while constructor/member dependencies used to create it can still be resolved from the existing container.

For objects that are created frequently or are an actual part of your dependency graph, I would still prefer registering a factory:

builder.RegisterFactory<MyClass>(
    resolver => () => new MyClass(
        resolver.Resolve<ISomeDependency>()),
    Lifetime.Singleton);

But for a truly one-off transient object, resolving an ad-hoc transient Registration is a compact option.

One thing to keep in mind: because this object is outside your normal registered lifetime graph, I would consider the caller responsible for its lifetime/disposal if it owns unmanaged/disposable resources.