Fixed GetEnumerator() method on mock #3999
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The Mock<IQueryable> needs to be configured to call the underlying collection's `GetEnumerator()` method every time it is invoked. As it is currently written, the method is only invoked once (during setup) to get a single value and that value is returned each time `GetEnumerator()` is called. This causes issues if the underlying data collection is changed by adding and/or removing items. Doing so results in the enumerator becoming stale and causes Invalid Operation Exceptions if you try to iterate through the IQueryable or call extension methods like `ToList()` or `ToArray()`
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Aug 25, 2022
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Currently the underlying data collection's
GetEnumerator()is only invoked once, and the resulting value is used every time the mockedDbSet'sGetEnumerator()method is invoked. The mockedDbSetneeds to be configured to retrieve a new enumerator each time the method is called by invoking the underlying data collection'sGetEnumerator()method. Otherwise the enumerator returned by the method will become invalid if the contents of the mockedDbSetchange.Since the example sets up the underlying data before configuring the mock, and doesn't make any subsiquent changes after that point, this doesn't cause any issues in the example. But if the same setup code is used in a unit test that involves modifying the contents of the DbSet, the code will throw
InvalidOperationExceptions anytime theDbSetis iterated through orToList()is called.