  We propose a general formalism to compute exact correlation functions for
Cardy's boundary states. Using the free-field construction of boundary states
and applying the Coulomb-gas technique, it is shown that charge-neutrality
conditions pick up particular linear combinations of conformal blocks. As an
example we study the critical Ising model with free and fixed boundary
conditions, and demonstrate that conventional results are reproduced. This
formalism thus directly associates algebraically constructed boundary states
with correlation functions which are in principle observable or numerically
calculable.
