Linq where子句问题
我想我不久前在某个地方看到过一个 where 子句的示例，它调用了一个给出 bool 结果的函数，但我找不到它了，所以我'我会概述我的问题。
我有一个集合
Dictionary< string, KeyValuePair < int, int >>
，我想在其中查询 string 键。表面上这很简单，但不幸的是，字符串（我无法控制）是网格单元的编码坐标。
查询是检索属于网格特定部分的条目（作为Dictionary类型）。放置函数调用 cells.Where(c => isWithinArea(c.Key, area)) 可以编译，但不起作用。该函数永远不会被调用。
我欢迎任何建议，让这项工作尽可能顺利进行。
I thought I'd seen somewhere a while back an example of where clause which called a function that gave a bool result ,and I can't find it again so I'll outline my problem.
I have a collection
Dictionary< string, KeyValuePair < int, int >>
in which I want to have a query for the string key. On the surface that is simple but unfortunately the string (over which I have no control) is an encoded co-ordinate of a grid cell.
The query is to retrieve entries (as the type of Dictionary) which fall into a certain part of the grid. Placing a function call cells.Where(c => isWithinArea(c.Key, area)) compiles but does not work. The function never gets called.
I would welcome any suggestions to make this work with a minimum of fuss.
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该函数从未被调用的最可能原因是，如果您“where-ing”的序列没有元素，或者您根本没有调用枚举器。 LINQ 是惰性求值的，这意味着在您开始
foreach或ToList()之前，您提供的任何表达式都不会被实际调用。The most likely reasons the function is never called would be if the sequence you're "where-ing" has no elements, or you are never invoking the enumerator at all. LINQ is lazy-evaluated, which means none of the expressions you've provided are actually invoked until you start to
foreachorToList().