Why am I getting DataClassesDataContext errors

I am getting many errors which state:
'DataClassesDataContext' does not contain a constructor that takes '0' arguments
 These errors refer to statements of: DataClassesDataContext db = new DataClassesDataContext(); which refer to where I open an SQL table such as with: LogData logdata = db.LogDatas.SingleOrDefault(p => p.Callsign == Callsign);
 Although I have nothing in these valid tables yet, I cannot understand why I am getting these error messages.  Please help me to understand what I am doing wrong so that I can fix it.
 Maurice