Does .NET have a built in IEnumerable for multiple collections?
- by Bryce Wagner
I need an easy way to iterate over multiple collections without actually merging them, and I couldn't find anything built into .NET that looks like it does that. It feels like this should be a somewhat common situation. I don't want to reinvent the wheel. Is there anything built in that does something like this:
public class MultiCollectionEnumerable<T> : IEnumerable<T>
{
private MultiCollectionEnumerator<T> enumerator;
public MultiCollectionEnumerable(params IEnumerable<T>[] collections)
{
enumerator = new MultiCollectionEnumerator<T>(collections);
}
public IEnumerator<T> GetEnumerator()
{
enumerator.Reset();
return enumerator;
}
IEnumerator IEnumerable.GetEnumerator()
{
enumerator.Reset();
return enumerator;
}
private class MultiCollectionEnumerator<T> : IEnumerator<T>
{
private IEnumerable<T>[] collections;
private int currentIndex;
private IEnumerator<T> currentEnumerator;
public MultiCollectionEnumerator(IEnumerable<T>[] collections)
{
this.collections = collections;
this.currentIndex = -1;
}
public T Current
{
get
{
if (currentEnumerator != null)
return currentEnumerator.Current;
else
return default(T);
}
}
public void Dispose()
{
if (currentEnumerator != null)
currentEnumerator.Dispose();
}
object IEnumerator.Current
{
get
{
return Current;
}
}
public bool MoveNext()
{
if (currentIndex >= collections.Length)
return false;
if (currentIndex < 0)
{
currentIndex = 0;
if (collections.Length > 0)
currentEnumerator = collections[0].GetEnumerator();
else
return false;
}
while (!currentEnumerator.MoveNext())
{
currentEnumerator.Dispose();
currentEnumerator = null;
currentIndex++;
if (currentIndex >= collections.Length)
return false;
currentEnumerator = collections[currentIndex].GetEnumerator();
}
return true;
}
public void Reset()
{
if (currentEnumerator != null)
{
currentEnumerator.Dispose();
currentEnumerator = null;
}
this.currentIndex = -1;
}
}
}
