Jeremy Stein - Brain

C# foreach two at a time

Do you want to iterate through a collection with a foreach, but retrieve two items at a time?

You can’t do it. The spec states specifically that the enumerator is inaccessible.

I supposed you could do something like this:

int[] a = {1, 2, 3, 4, 5, 6};

int previousVal = -1;
bool odd = false;
foreach (int currentVal in a)
{
  odd = ! odd;
  if (odd)
  {
    previousVal = currentVal;
    continue;
  }
  Console.WriteLine(String.Format("{0}, {1}",
    previousVal, currentVal));
}

March 29, 2006 1 Comment.

One Comment

1. Miguel replied:
   

   You can do this sort of thing by working directly with the enumerator.
   Not sure if this will work with older versions of C#, you would have to put in the actual object type instead of “var” for one.

   var enumerator = a.GetEnumerator();
   while (enumerator.MoveNext()){
       var current = enumerator.Current;
       if (enumerator.MoveNext()){
           var afterCurrent = enumerator.Current;
           //here you can access "current" & "afterCurrent"
       }else{
           //here you can only access "current", there is no item after this.
       }
   }

   October 6th, 2011 at 5:25 am. Permalink.

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