How does LINQ behave when query execution order is unintentionally reversed due to deferred execution?

Deferred execution can cause unexpected order changes when side effects or external state modifications exist before enumeration.

LINQ queries are not executed at declaration time but at enumeration time. If external state changes between query definition and execution, results may differ from expectation. This becomes especially problematic when queries depend on mutable variables or when multiple transformations are chained before materialization. The logical order in code is not always the execution order in runtime.