c# - Callback syncronization between threads -

i want wait on getvalues.get method , return values syncronously caller. serverdataprovider, bookdatafetcher classes external mycode, on have no control. on how achieve appreciated.

namespace test { class program {     static void main(string[] args)     {         getvalues val = new getvalues();         val.get("books", datahandler);         console.readkey();     }      static void datahandler(ilist<string> values) {     } }  class getvalues {     public delegate void datahandler(ilist<string> values);     public event datahandler onreceivedatahandler;      public void get(string colname, datahandler handler)     {         onreceivedatahandler += handler;         getdatafromserver svr = new getdatafromserver();         svr.onreceivedatahandler += onreceivedata;         svr.getdata(colname);     }      // callback handler     private void onreceivedata(ilist<string> values) {         onreceivedatahandler(values);     } }  class getdatafromserver {     internal delegate void datahandler(ilist<string> values);     internal event datahandler onreceivedatahandler;      internal void getdata(string columnname)     {         serverdataprovider datafetcher = new serverdataprovider();         datafetcher.onreceivedatahandler += onreceivedata;         task.factory.startnew(() => datafetcher.getdatafromserver(columnname));     }      // callback handler     private void onreceivedata(ilist <string> values) {         onreceivedatahandler(values);     } }  class serverdataprovider {     internal delegate void datahandler(ilist<string> values);     internal event datahandler onreceivedatahandler;      public void getdatafromserver(string columnname)     {         bookdatafetcher b = new bookdatafetcher();         b.onreceivedatahandler += onreceivedata;         task.factory.startnew(() => b.getbookdata(columnname));     }      // calback handler     private void onreceivedata(ilist<string> values)     {         onreceivedatahandler(values);     } }  class bookdatafetcher {     internal delegate void datahandler(ilist<string> values);     internal event datahandler onreceivedatahandler;      public void getbookdata(string col)     {         thread.sleep(5000);         onreceivedatahandler(new list<string> {"book1", "book2"});     } } 

}

what asking can achieved using methodimplattribute

 [methodimplattribute(methodimploptions.synchronized)]   public void methoda()