1, LINQ to SQL Tutorial - guogangj - blog Park .html ( https://www.cnblogs.com/guogangj/archive/2013/02/22/2920961.html#m2 )
ZC: there is an example of the value returned by yield to explain the phenomenon of delayed execution, also talked about two kinds of catch not unusual solution: (1) try statement catch the actual use of (2) and then wrapped in a layer of function [actually is ∵ layer function uses a function of the data inside]
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