visual studio - Update configuration file vb.net programmatically -

i have created form shows number of settings held in exe.config file, user able change. example have text box named txtreadserver populate setting readserver in following manner: m_configurationform.txtreadserver.text = my.settings.readserver

from have read on , other forums, need use configurationmanager in order update these setting in exe.config @ runtime. problem when try following: dim config configuration = configurationmanager.openexeconfiguration(configurationuserlevel.none) visual studio seems not know configuration object is. have tried add imports system.configuration @ top of class, word configuration still highlighted in dreaded red!

any - or suggestions on best way allow users configure app gratefully received.

thanks,

paul.

add reference in project system.configuration.