IDictionaryEnumerator is not an iterator interface type?
I'm trying to port some code that uses Hashtable to an environment that doesn't have this class. So I thought about not messing with the code and just create my own Hashtable from Dictionary , like this:
public class Hashtable : Dictionary<Object, Object> {
// ...
new public IDictionaryEnumerator GetEnumerator() {
var ie = base.GetEnumerator();
while (ie.MoveNext())
yield return new DictionaryEntry(ie.Current.Key, ie.Current.Value);
}
}
I'm getting this error:
error CS1624: The body of 'System.Collections.Hashtable.GetEnumerator()' cannot be an iterator block because 'System.Collections.IDictionaryEnumerator' is not an iterator interface type
Well, but IDictionaryEnumerator inherits from IEnumerator .
The odd thing is that if I just return (IDictionaryEnumerator)base.GetEnumerator(); the code compiles (but fails during runtime in the foreach loop).
I don't understand what this error is telling me and don't know how to properly implement this.
Iterator blocks are rewritten by the compiler into classes that implement IEnumerable or IEnumerator ; the compiler doesn't know how to generate a class that implement IDictionaryEnumerator , so you can't use an iterator block to implement that interface.
A possible workaround is to provide your own implementation of IDictionaryEnumerator :
class Hashtable : Dictionary<object, object>
{
new public IDictionaryEnumerator GetEnumerator()
{
return new DictionaryEnumerator(base.GetEnumerator());
}
struct DictionaryEnumerator : IDictionaryEnumerator
{
private Enumerator _en;
public DictionaryEnumerator(Dictionary<object, object>.Enumerator en)
{
_en = en;
}
public object Current
{
get
{
return Entry;
}
}
public DictionaryEntry Entry
{
get
{
var kvp = _en.Current;
return new DictionaryEntry(kvp.Key, kvp.Value);
}
}
public bool MoveNext()
{
bool result = _en.MoveNext();
return result;
}
public void Reset()
{
throw new NotSupportedException();
}
public object Key
{
get
{
var kvp = _en.Current;
return kvp.Key;
}
}
public object Value
{
get
{
var kvp = _en.Current;
return kvp.Value;
}
}
}
}