c# - how to avoid in WCF service interface to implementing either synchronous or asynchronous Method -

i have implemented wcf services, have defined synchronize method following;

[servicecontract] public interface imarketingcampaigntype {     [operationcontract]     list<marketingcampaigntypedata> getallcampaigntypes();      [operationcontract]     marketingcampaigntypedata getcampaigntypebyid(int campaigntypeid);      [operationcontract]     marketingcampaigntypedata createnewcampaigntype();      [operationcontract]     marketingcampaigntypedata editcampaigntype();      [operationcontract]     bool deletecampaigntype(); } 

now on client side when configure service choosing 'add service reference' in visual studio under project, interface generated under namespace 'app.client.proxies.marketingcampaigntypeserviceref'

but when implement interface getting 2 of each methods each implementation 1 synchronous , other asynchronous. know in client choose 1 want implement question can can control 1 allowing or have 1 type of method instead of two?

here interface implementation of service

 public class marketingcampaigntypeclient : imarketingcampaigntype  {     public marketingcampaigntypedata createnewcampaigntype()     {         throw new notimplementedexception();     }      public task<marketingcampaigntypedata> createnewcampaigntypeasync()     {         throw new notimplementedexception();     }      public bool deletecampaigntype()     {         throw new notimplementedexception();     }      public task<bool> deletecampaigntypeasync()     {         throw new notimplementedexception();     }      public marketingcampaigntypedata editcampaigntype()     {         throw new notimplementedexception();     }      public task<marketingcampaigntypedata> editcampaigntypeasync()     {         throw new notimplementedexception();     }      public marketingcampaigntypedata[] getallcampaigntypes()     {         throw new notimplementedexception();     }      public task<marketingcampaigntypedata[]> getallcampaigntypesasync()     {         throw new notimplementedexception();     }      public marketingcampaigntypedata getcampaigntypebyid(int campaigntypeid)     {         throw new notimplementedexception();     }      public task<marketingcampaigntypedata> getcampaigntypebyidasync(int campaigntypeid)     {         throw new notimplementedexception();     } 

make sure, have unchecked in serviceconfig: