Link error when use functions of PGtypes

Hi:

I installed PostgreSQL9.0 from EnterpriseDB with“one click installer” in
windows 7 & 32bit.

and use microsoft visual studio 2010 c++.

I added the libpq.lib to the link property of the project, also included the
lib folder and path.

Successfully compiled .c and .cpp file after transfer .pgc file to .c file
using ECPG.

But it always have errors like this when link:

error LNK2019: unresolved external symbol _PGTYPESinterval_new referenced in
function.

And all the function PGTYPEStimestamp and PGTYPEsinterval can cause the
same error.

Does someone can help me?

Thanks.

Fanbin