Если SqlDependency используется без указания значения для Оptions, то перед выполнением команды, добавленной в экземпляр SqlDependency, необходимо вызвать метод SqlDependency.Start().

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When using SqlDependency without providing an options value, SqlDependency.Start() must be called prior to execution of a command added to the SqlDependency instance.

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