You can roll your own ZipMany instance which manually iterates each of the enumerations. This will likely perform better on larger sequences than those using GroupBy
after projecting each sequence:
public static IEnumerable<TResult> ZipMany<TSource, TResult>(
IEnumerable<IEnumerable<TSource>> source,
Func<IEnumerable<TSource>, TResult> selector)
{
// ToList is necessary to avoid deferred execution
var enumerators = source.Select(seq => seq.GetEnumerator()).ToList();
try
{
while (true)
{
foreach (var e in enumerators)
{
bool b = e.MoveNext();
if (!b) yield break;
}
// Again, ToList (or ToArray) is necessary to avoid deferred execution
yield return selector(enumerators.Select(e => e.Current).ToList());
}
}
finally
{
foreach (var e in enumerators)
e.Dispose();
}
}