Groups the elements of a sequence according to a specified keyselector function and creates a result value from each group and its key.
依据指定的索引键选择器函式来群组序列的项目,并从每个群组及其索引键建立结果值。
2
Rules with a tag selector as the key.
标签选择器作为键的规则。
3
The engine evaluates each rule from right to left, starting from the rightmost selector (called the "key") and moving through each selector until it finds a match or discards the rule.