对于C#的query查询语法，其可读性和可维护性要比原来的loop操作好得多
例子：
同样是创建个二维元组，并对其元组按到原点的距离进行倒序排序，用query 语法的表达形式要比原始的循环做法来的更易读、更易于维护，并且省去了用于存储中间过程的额外临时变量（例子中原始方法用的 storage对象）
//原始的循环方法
private static IEnumerable<Tuple<int, int>> ProduceIndices3()
{
var storage = new List<Tuple<int, int>>();
for (int x = 0; x < 100; x++)
for (int y = 0; y < 100; y++)
if (x + y < 100)
storage.Add(Tuple.Create(x, y));
storage.Sort((point1, point2) =>
(point2.Item1*point2.Item1 +
point2.Item2 * point2.Item2).CompareTo(
point1.Item1 * point1.Item1 +
point1.Item2 * point1.Item2));
return storage;
}
//query syntax
private static IEnumerable<Tuple<int, int>> QueryIndices3()
{
return from x in Enumerable.Range(0, 100)
from y in Enumerable.Range(0, 100)
where x + y < 100
orderby (x*x + y*y) descending
select Tuple.Create(x, y);
}
//using the method call syntax
private static IEnumerable<Tuple<int, int>> MethodIndices3()
{
return Enumerable.Range(0, 100).
SelectMany(x => Enumerable.Range(0,100),
(x,y) => Tuple.Create(x,y)).
Where(pt => pt.Item1 + pt.Item2 < 100).
OrderByDescending(pt =>
pt.Item1* pt.Item1 + pt.Item2 * pt.Item2);
}