Information Technology Reference
In-Depth Information
Using the IEnumerator Interface
This section will start by looking at the first in the preceding list: the non-generic interface
form. This form of enumerator is a class that implements the
IEnumerator
interface. It is called
non-generic
because it does not use C# generics.
The
IEnumerator
interface contains three function members:
Current
,
MoveNext
, and
Reset
.
Current
is a property that returns the item at the current position in the sequence.
-
It is a read-only property.
It returns an object of type
object
, so an object of any type can be returned.
-
MoveNext
is a method that advances the enumerator's position to the next item in the
collection. It also returns a Boolean value, indicating whether the new position is a valid
position or is beyond the end of the sequence.
-
If the new position is valid, the method returns
true
.
If the new position is not valid (i.e., it's at the end), the method returns
false
.
-
-
The initial position of the enumerator is
before
the first item in the sequence.
MoveNext
must be called
before
the first access of
Current
.
Reset
is a method that resets the position to the initial state.
Figure 20-2 illustrates a collection of three items, which are shown on the left of the figure,
and its enumerator, which is shown on the right. In the figure, the enumerator is an instance of
a class called
ArrEnumerator
.
Figure 20-2.
The enumerator for a small collection
