c# - 'System.Data.Entity.DbSet<Survey.Models.Survey>.DbSet()' is inaccessible due to its protection level -

can me understand error? i'm getting on line new dbset<survey>(); in block code

    public dbset<survey> getallsurveys ( )     {         dbset<survey> allsurveys = new dbset<survey>();         using ( sqlcommand cmd = new sqlcommand("getallsurveys", this._conn) )         {            cmd.commandtype = commandtype.storedprocedure;            this._conn.open();             using ( sqldatareader datareader = cmd.executereader() )            {                 while ( datareader.read() )                 {                     survey srv = new survey { id = datareader.isdbnull(0) ? default(int) : datareader.getint32(0),                                               title = datareader.isdbnull(1) ? string.empty: datareader.getstring(1) };                     allsurveys.add(srv);                 }            }            this._conn.close();         }         return allsurveys;     } 

what's strange i'm not getting when create dbset<t> right below:

    public dbset<question> getquestionsbysurveyid ( int survid )     {         sqlcommand cmd = new sqlcommand("getquestionsbysurveyid", this._conn);         cmd.commandtype = commandtype.storedprocedure;         cmd.parameters.addwithvalue("@id", survid);         this._conn.open();         dbset<question> thesequestions = (dbset<question>)cmd.executescalar();         this._conn.close();         return thesequestions;     } 

has no errors associated it. what's difference between these two?