//IEnumerable<int> first = { 1, 2, 3, 4, 5 }
//IEnumerable<int> second = { 6, 7, 8, 9, 10 }
IEnumerable<int> result = first.Append(second)
//result = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }
//IEnumerable<int> first = { 6, 7, 8, 9, 10 }
//IEnumerable<int> second = { 1, 2, 3, 4, 5 }
IEnumerable<int> result = first.Append(second)
//result = { 6, 7, 8, 9, 10, 1, 2, 3, 4, 5 }