c# - How to use ConfigurationManager -

i want use app.config storing setting. tried use next code getting parameter config file.

private string getsettingvalue(string paramname) {     return string.format(configurationmanager.appsettings[paramname]); } 

i added system.configuration (i used separate class), , in app.config file have:

<?xml version="1.0" encoding="utf-8" ?> <configuration>   <startup>      <supportedruntime version="v4.0" sku=".netframework,version=v4.5" />   </startup>   <appsettings>     <add key ="key1" value ="sample" />   </appsettings> </configuration> 

but got error while trying use configurationmanager - configurationmanager can't exist in such context, added system.configuration. or did miss something?

edit:

class config (full view)

using system; using system.collections.generic; using system.linq; using system.text; using system.threading.tasks; using system.configuration;  namespace browser {     class configfile     {         private string getsettingvalue(string paramname)         {             return string.format(configurationmanager.appsettings[paramname]);         }     } } 

edit2

add how looks

this means problem not during using configurationmanger before - program "says" "doesn't know such element" understand error - "element configurationmanager" doesn't exist in such context"

edit3

edit 4

okay, took me while see this, there's not way compiles:

return string.(configurationmanager.appsettings[paramname]); 

you're not calling method on string type. this:

return configurationmanager.appsettings[paramname]; 

the appsettings kvp returns string. if name doesn't exist, return null.

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based on edit have not yet added reference system.configuration assembly project you're working in.