Question

here is i am trying to work.

List<MasterEmployee > masterEmployee = new List<MasterEmployee >();
masterEmployee = MasterEmployee.GetAll("123"); //connecting db and returning a list...


  foreach (MasterEmployee item in masterEmployee)
   {
      foreach (Registration reg in item.Registration) //<<<error here...
      {
           //
      }
  }

error here:

Error   2   foreach statement cannot operate on variables of type Registration because Registration does not contain a public definition for 'GetEnumerator'

i have a class called MasterEmployee and in it i have a with few props and few methods on it

 [Serializable]
    public class MasterEmployee 
    {

        //few props omitted  ....

        protected Registration _registration;
        [CopyConstructorIgnore]
        public Registration Registration
        {
            get
            {
                return _registration;

            }
            set
            {
                this._registration = value;
            }
        }
        protected User _user;
        [CopyConstructorIgnore]
        public User MyUser
        {
            get
            {
               return _user;
            }
            set
            {
                this._user= value;
            }
        }

        protected Student _student;
        [CopyConstructorIgnore]
        public Student Student
        {
            get
            {
                return _student;
            }
            set
            {
                this._student = value;
            }
        }
}

Answer 1

The explanation provided in the error message is clear enough. You are trying to iterate item.Registration, which is an instance of Registration. However, Registration is not derived from an iterable type, and does not implement the GetEnumerator function required for custom iterable types. So it cannot be iterated using a foreach loop.

But I believe either your naming conventions are incorrect, or you have misunderstood your data model. Why would a Registration instance ever contain a collection of Registration instances? If an item can have multiple Registration instances associated with it, then the property should be called something like item.Registrations, and it should not be of type Registration, it should be a list/collection type that contains Registration instances.