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I did below work
class Program
{
class GenEnumerator<T> : IEnumerable
{
public T[] Values { get; set; }
public IEnumerator GetEnumerator()
{
for (int i = 0; i < Values.Length; i++)
yield return Values[i];
}
}
static void Main(string[] args)
{
GenEnumerator<string> g = new GenEnumerator<string>();
g.Values = new string[] { "a", "b", "c", "d", "e" };
g.GetEnumerator().MoveNext();
Console.WriteLine(g.GetEnumerator().Current);
Console.ReadKey();
}
}
g.GetEnumerator().Current is always null.
but if I do this - var a = g.GetEnumerator();
the Current proeperty gets a value and works fine
Does it imply that I have to explicitly inherit the class from IEnumerator and implement its methods and property if I want to use Current without a IEnumerator type variable?
Thanks, Roy
684
The element in the collection at the current position of the enumerator. The following code example demonstrates the implementation of the IEnumerator interfaces for a custom collection. In this example, Current is not explicitly called, but it is implemented to support the use of foreach ( for each in Visual Basic).
Returns an enumerator that iterates through a collection. An IEnumerator object that can be used to iterate through the collection. The following code example demonstrates the implementation of the IEnumerable interfaces for a custom collection.
An IEnumerator object that can be used to iterate through the collection. The following code example demonstrates the implementation of the IEnumerable interfaces for a custom collection. In this example, GetEnumerator is not explicitly called, but it is implemented to support the use of foreach ( For Each in Visual Basic).
As per code, we are now passing IEnumerable. Let's check out the output: As per output, it is clear that IEnumerable does not remember the current state it was processing. Thus it starts processing back from the 1st index. In this article, we learned how to and when to use IEnumerable & IEnumerator.
You're creating new instances of GenEnumerator everytime by calling GetEnumerator, that's why your Current is null. Instead store it in a field and use that.
var e = g.GetEnumerator();
if(e.MoveNext())
{
var current = e.Current;
}
This is because in order for the Current to become non-null, you need to call MoveNext() on the same object.
Your current code calls MoveNext() on a temporary object. Here is what's going on when you call
g.GetEnumerator().MoveNext()`;
Console.WriteLine(g.GetEnumerator().Current);
GetEnumerator() returns an object x
x.MoveNext() is performedx becomes eligible for garbage collection, because it is not referenced from any variable in your program.g.GetEnumerator().Current, a new object y is returnedy.Current is made, returning null, because there was no call of MoveNext on object y
When you add a variable a, however, you call MoveNext and Current on the same object, fixing the problem:
GetEnumerator() returns an object x, which is assigned to variable a
a.MoveNext() is performeda.Current is performed
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