Your .GroupBy(y => y.L​​anguageCode).ToDictionaryAsync(y => y.Key, y => y.Select(z => z.Name)); 无法转换为 SQL.EF Core 3.0 将抛出异常以确保您知道 Units 中的所有记录将在分组并映射到字典之前从数据库中获取.

Your .GroupBy(y => y.LanguageCode).ToDictionaryAsync(y => y.Key, y => y.Select(z => z.Name)); cannot be converted to SQL. EF Core 3.0 will throw exception to make sure you know that all records in Units will be fetched from database before grouping and map to Dictionary.

这是 EF Core 3.0 中最重大的变化.https://docs.microsoft.com/en-us/ef/core/what-is-new/ef-core-3.0/break-changes

It's top breaking change in EF Core 3.0. https://docs.microsoft.com/en-us/ef/core/what-is-new/ef-core-3.0/breaking-changes