how to add new connection string in web.config run time programatically in asp.net? -

i working on construction erp. when user adds new structure have create new database each structure.whether possible using script?

at same time creating new database each structure necessary create 1 additional connection string in web.config file

very first trying add new connection string in config file.for have written code.but gives me error.

 string path = server.mappath(@"web.config"); 'or' string path = server.mappath("~/web.config");         var configuration = webconfigurationmanager.openwebconfiguration(path);         var section = (connectionstringssection)configuration.getsection("connectionstrings");         section.connectionstrings.add(new connectionstringsettings(txtstructname.text, txtstructname.text, "system.data.sqlclient"));         configuration.save(); 

error :the relative virtual path not allowed here.

help me solve problem.....

you shouldn't need specify web.config.

just do

webconfigurationmanager.openwebconfiguration("~");