c# - Call a constant name from web.config -

in webserivce coding, want call constant name web.config. have code :

namespace service.appcode.common.service {     [servicecontract(namespace = constants.namespace)]     public interface iservice1     {         [operationcontract]         void dowork();     } } 

and code:

namespace service.appcode.common {     public class constants     {         public const string namespace = configurationmanager.appsettings["defaulip"];     } } 

it :

the expression being assigned 'service.appcode.common.constants.namespace' must constant

is possible call web.config?

constants defined @ compile-time , embedded directly resulting code, they're not initialized when application executes. (and can't change, unlike config value can change.)

however, looking @ this...

public class constants {     public readonly static string namespace =          configurationmanager.appsettings["defaulip"]; } 

it looks want static immutable value. that's easy enough...

public class constants {     public static string namespace     {         { return configurationmanager.appsettings["defaulip"]; }     } } 

that read value dynamically configuration time it's invoked. , since it's getter, it's read-only. if want read config once, cache value:

public class constants {     private static string _namespace = null;     public static string namespace     {                 {             if (_namespace == null)                 _namespace = configurationmanager.appsettings["defaulip"];             return _namespace;         }     } }