private object GetSingleInstance(Type registrationType, object target, string key)
{
if (registrationType == null)
{
return(null);
}
lock (_lock)
{
var registrations = _registrations.Where(x => x.RegistrationType == registrationType && x.Key == key);
var registrationsCount = registrations.Count();
if (registrationsCount > 1)
{
// More than 1 implementation type registerd for this registration type.
// No idea which one to pick.
throw new ContainerException(ContainerErrorCodes.MultipleImplementationTypesRegistered,
$"Cannot get a single instance for registration type {registrationType.FullName} because multiple implementation types have been registered for this registration type.");
}
if (registrationsCount == 1)
{
// There is exactly 1 implementation type registered for this registration type.
// This is ok, so construct it.
var registration = registrations.First();
if (registration is TypeRegistrationBase typeRegistration)
{
return(GetImplementationInstance(typeRegistration, target));
}
if (registration is HandlerRegistration handlerRegistration)
{
return(handlerRegistration.Handler(new HandlerParameter(this, target)));
}
}
return(_containerHelper.GetDefault(registrationType));
}
}