When you have to introduce a temporary range variable for the right side (inner) sequence before the join operation.

必须在联接操作之前为右侧(内部)序列引入一个临时范围变量。

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If the range variable is explicitly typed, make sure that the type is either the same as, or implicitly convertible from, the type of the elements in the collection it iterates.

如果范围变量是显式类型的，请确保该类型与循环访问的集合中的元素类型相同或可从该类型隐式转换。

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If the range variable is explicitly typed, make sure that the type is either the same as, or implicitly convertible from, the type of the elements in the collection it iterates.

如果范围变量是显式类型的，请确保该类型与循环访问的集合中的元素类型相同或可从该类型隐式转换。

youdao