c#属性一点疑问

public class A
    {
        //定义一个b属性
        public B b
        {
            get
            {
                return new B();  //每次get均调用
            }
        }
        //public B b = new B();   只调用一次
    }

return new B();

public RelayCommand EditCommand {
            get {   
               return new RelayCommand(() => {                  
                          CurrentEmployee.BeginEdit();
                      });
            }
        }