List<T>的交并差集操作操作

这个操作应该是比较基础的了，平时用得也比较少，所以写在这里提醒自己Framework已经提供了这样的功能了：

static void Main(string[] args)
{
    var left = new List<SampleData> { SampleData.OwnedByLeft, SampleData.OwnedByBoth };
    var right = new List<SampleData> { SampleData.OwnedByRight, SampleData.OwnedByBoth };

    var intersection = left.Intersect(right);
    Console.WriteLine("The intersection of left and right is: {0}", string.Join(",", intersection));//output: OwnedByBoth

    var differenceSetOfLeft = left.Except(right);
    Console.WriteLine("The difference set of left to right is: {0}", string.Join(",", differenceSetOfLeft));//output: OwnedByLeft

    var differenceSetOfRight = right.Except(left);
    Console.WriteLine("The difference set of right to left is: {0}", string.Join(",", differenceSetOfRight));//output: OwnedByRight

    var unionSet = right.Union(left);
    Console.WriteLine("The union set of left and right is: {0}", string.Join(",", unionSet));//output: OwnedByRight, OwnedByBoth, OwnedByLeft

}

private enum SampleData
{
    OwnedByLeft,
    OwnedByBoth,
    OwnedByRight,
}

以上的示例中采用的是enum（同int），如果是对自定义的类型（如class、structure），则需要实现IEquatable<T>接口方能这样用。