c# - Extending functionality through interfaces -

i have implemented interface iservice inherits functionality series of other interfaces , serves common ground many different services.

each of these services being described interface, example:

public interface iserviceone : iservice  {   //... }  public class serviceone : iserviceone {   //... } 

everything point works expected:

iserviceone serviceone = new serviceone(); iservicetwo servicetwo = new servicetwo();  

what have add big list of constants (public variables) each of these services different per service type (for example, iserviceone have different constants iservicetwo, there constants in iserviceone not exist in iservicetwo, etc).

what i'm trying achieve that:

iserviceone serviceone = new serviceone(); var someconstantvalue = serviceone.const.someconstant; 

just because variables differ of service type decided implement interface each of them:

public interface iserviceoneconstants {    //... } 

and broaden iservice definition:

public interface iserviceone : iservice, iserviceoneconstants  {   //... }  public class serviceone : iserviceone {   //... } 

the problem have don't know how implement concrete class iserviceoneconstants. time 1 of variables (we called them constants here) called has instantiated, though of static class cannot expose static class's functionality through interface. tried singleton , expose instance via public non-static wrapper:

public class singleton : iserviceoneconstants {     private static singleton _instance;      private singleton()     {         someconstant = "some value";     }      public static singleton instance     {                 {             if (_instance == null)             {                 _instance = new singleton();             }             return _instance;         }     }      public string someconstant { get; set; }      public singleton const     {                 {             return instance;         }     } } 

i adjusted iserviceoneconstants that:

public interface iserviceoneconstants {    singleton const { get; } } 

but when call this:

iserviceone serviceone = new serviceone(); var someconstantvalue = serviceone.const.someconstant; 

i null reference exception, .const null.

what missing here?

you helped confused possible, naming different stuff same name ;)

so, first... you're trying access singleton instance through instance property:

public singleton const     {                 {             return instance;         }     } 

then using like:

serviceone.const 

but variable never assigned. in order assign it, should make instance of singleton class, assign serviceone.const property , might use it.

what need this:

public class serviceone : iserviceone {    public singleton const    {              {          return singleton.instance;       }    } }