How to read the Section from Config file from c# code -

while reading config section through c# , getting error in line 1.

the application relative virtual path '~' not allowed here.

system.configuration.configuration config =     system.web.configuration.webconfigurationmanager.openwebconfiguration("~");   systemwebsectiongroup grp = (systemwebsectiongroup)config.getsectiongroup("system.web"); 

my guess value of "~" not allowed when calling openwebconfiguration, that's guess reading error message. documentation openwebconfiguration (http://msdn.microsoft.com/en-us/library/ms151456(v=vs.110).aspx) says pass null if want root web.config.