Can a generator be connected to a 220v outlet to provide emergency power for a house?

If an electric generator with 220v single phase output is connected to a home electrical system through a 220v outlet and the main breaker in the breaker box is turned off to disconnect the house from the city power, will the generator then power the house without feeding power back to the city power grid?

Could an existing outlet be used, such as an electric dryer outlet, if the load from the house was first adjusted to ensure that it was less than the breaker capacity on the dryer outlet?

What are the dangers to doing this (aside from those related directly to generating your own power)?

What is the correct way to do this without spending a thousand or more dollars on automatic transfer switches and such?
The house in question has 200A service and would be provided with a 12kW generator. Most lighting is CF so excepting appliances normal power usage profile for the house is well within the generators capacity.

When running on emergency power major power consuming appliances (ovens, stove, dryer, AC) would not be used or would be engaged only after ensuring that sufficient capacity was available.