About set up connection string

Question

Respected Experts
I have done 2 windows application and used following connection sting in first one to deploy application to client side so that we need not to install database to client side here dm=folder name in which i am putting .mdf file of my hm database, it is running successfully
dm folder is in set up project and copying mdf files after stopping service of sql server, in this project only forms are here

"Data Source=.\\SQLEXPRESS;AttachDbFilename=" +Application.StartupPath + "\\dm\\hm.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True"


but when same i am trying to do in another windows application in  which there is datalayer class(class library) it is giving problem
please help me out to find solution , i have also run thread for same problem before months and also on various forums but still not satisfied
please help me out