O(n²) loop in OpenXmlElementEqualityComparer.cs

[SimonCropp]

  for (int i = 0; i < x.ExtendedAttributes.Count(); i++)  // Count() re-enumerates each iteration
  {
      if (!x.ExtendedAttributes.ElementAt(i).Equals(y.ExtendedAttributes.ElementAt(i)))  // ElementAt is O(n)

Count() is called every loop iteration (re-enumerates), and ElementAt(i) is O(n) on IEnumerable, making the entire loop O(n³). Fix: materialize to a list/array once, or use SequenceEqual / paired foreach with two enumerators.

[github-actions]

Test Results

    68 files  + 1      68 suites  +1   1h 41m 9s ⏱️ + 6m 30s
 2 068 tests ± 0   2 065 ✅ ± 0   3 💤 ±0  0 ❌ ±0 
37 887 runs  +22  37 845 ✅ +22  42 💤 ±0  0 ❌ ±0 

Results for commit 37292f5. ± Comparison against base commit 40ad85b.