C # What is the difference between IEnumerable and IEnumerator?

The IEnumerable interface and the IEnumerator interface are very important interfaces in. NET. What are the differences between them?

1. in short, IEnumerable is a declarative interface. The class that declares the implementation of this interface is "iteratable enumerable", but it does not explain how to implement iterator ). the code is implemented as follows:

Public interface IEnumerable
{
IEnumerator GetEnumerator ();
}
2. The IEnumerator interface is an implementation interface. It declares that the class implementing this interface can be used as an iterator. Its code is implemented as follows:

Public interface IEnumerator
{
Object Current {get ;}

Bool MoveNext ();
Void Reset ();
}

3. To support Foreach traversal, a collection must implement IEnumerable and return the iterator object in a certain way: IEnumerator.

How can we implement these two interfaces? The Code is as follows:

Assume that there is a Person class, which has two attributes: FirstName and LastName.

Public class Person
{
Public string FirstName {get; set ;}
Public string LastName {get; set ;}
Public Person (string firstName, string lastName)
{
This. FirstName = firstName;
This. LastName = lastName;
}
}

In addition, the People class is used to implement the IEnumerable and IEnumerator interfaces.

// Implement the IEnumerable Interface

Public class People: IEnumerable

{

Public Person [] pers;

Public People (Person [] ps)

{

This. pers = ps;

}

Public IEnumerator GetEnumerator ()

{

// Foreach (Person p in pers)

//{

// Yield return p;

//}

Return new People1 (pers );

}

}

// Implement the IEnumerator Interface

Public class People1: IEnumerator
{
Public Person [] pers;
Public People1 (Person [] per)
{
This. pers = per;
}
Int position =-1;

Public bool MoveNext ()
{
Position ++;
Return position <pers. Length;
}
Public void Reset ()
{
Position =-1;
}
Public object Current
{
Get
{
Try
{
Return pers [position];
}
Catch (IndexOutOfRangeException ex)
{
Throw new InvalidOperationException ();
}
}
}
}