c# - How to iterate through two IEnumerables simultaneously? -

i have enumerables ienumerable<a> list1 , ienumerable<b> list2 , iterate through them simultaneously like:

foreach((a, b) in (list1, list2)) {   // use , b } 

if not contain same number of elements, exception should thrown.

what best way this?

here's implementation of operation, typically called zip:

using system; using system.collections.generic;  namespace so2721939 {     public sealed class zipentry<t1, t2>     {         public zipentry(int index, t1 value1, t2 value2)         {             index = index;             value1 = value1;             value2 = value2;         }          public int index { get; private set; }         public t1 value1 { get; private set; }         public t2 value2 { get; private set; }     }      public static class enumerableextensions     {         public static ienumerable<zipentry<t1, t2>> zip<t1, t2>(             ienumerable<t1> collection1, ienumerable<t2> collection2)         {             if (collection1 == null)                 throw new argumentnullexception("collection1");             if (collection2 == null)                 throw new argumentnullexception("collection2");              int index = 0;             using (ienumerator<t1> enumerator1 = collection1.getenumerator())             using (ienumerator<t2> enumerator2 = collection2.getenumerator())             {                 while (enumerator1.movenext() && enumerator2.movenext())                 {                     yield return new zipentry<t1, t2>(                         index, enumerator1.current, enumerator2.current);                     index++;                 }             }         }     }      class program     {         static void main(string[] args)         {             int[] numbers = new[] { 1, 2, 3, 4, 5 };             string[] names = new[] { "bob", "alice", "mark", "john", "mary" };              foreach (var entry in numbers.zip(names))             {                 console.out.writeline(entry.index + ": "                     + entry.value1 + "-" + entry.value2);             }         }     } } 

to make throw exception if 1 of sequences run out of values, change while-loop so:

while (true) {     bool hasnext1 = enumerator1.movenext();     bool hasnext2 = enumerator2.movenext();     if (hasnext1 != hasnext2)         throw new invalidoperationexception("one of collections ran " +             "out of values before other");     if (!hasnext1)         break;      yield return new zipentry<t1, t2>(         index, enumerator1.current, enumerator2.current);     index++; }