[Solved]-EF: Can I have single point for lambda to class instance conversion?-LINQ,C#

yes, you can do:

expression<func<person, personentity>> converttopersonentity() {
  return x => new personentity { id = x.id, name = x.name };
}

...and then:

personentity getbyid(int id) {
  var exp = converttopersonentity();
  return db.person.firstordefault(exp);
}