SymmetricDifference

Returns the symmetric difference betweend two collections.

• Use IEnumerable.Except() to only return elements in one enumerable object and not the other.
• Use IEnumerable.Union() to combine the result of applying that to each object.

using System.Collections.Generic;
using System.Linq;

public static partial class _30s 
{
  public static IEnumerable<T> SymmetricDifference<T>(IEnumerable<T> a, IEnumerable<T> b) 
  {
    return a.Except(b).Union(b.Except(a));
  }
}

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

_30s.SymmetricDifference(a, b); // { 3, 5, 4 }