# System.InvalidOperationException: 无法对在 Select 中也使用的集合导航上的 Include 使用拆分查询。请在 Include 之前调用 AsSplitQuery() 或移除 Select。

- **ID:** `dotnet/ef-core-query-split-query-exception`
- **领域:** dotnet
- **类别:** data_error
- **验证级别:** ai_generated
- **修复率:** 90%

## 根因

当 LINQ 查询在导航属性上组合使用 'Include' 和投影同一导航的 'Select' 时，与拆分查询执行模式冲突，Entity Framework Core 会抛出此异常。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| Entity Framework Core 7.0 | active | — | — |
| Entity Framework Core 8.0 | active | — | — |

## 解决方案

1. ```
   在查询链中第一个 'Include' 之前放置 'AsSplitQuery()'：'var result = context.Orders.AsSplitQuery().Include(o => o.Items).Where(o => o.Id == 1).ToList();'
   ```
2. ```
   用显式投影相关数据的 'Select' 替换 'Include'：'var result = context.Orders.Where(o => o.Id == 1).Select(o => new { o.Id, Items = o.Items.Select(i => i.Name) }).ToList();'
   ```

## 无效尝试

- **** — Adding 'AsSplitQuery()' after 'Include' does not fix the issue; it must be placed before the Include chain. (80% 失败率)
- **** — Removing 'Include' and relying solely on lazy loading may cause N+1 query problems and performance degradation. (65% 失败率)
- **** — Switching to 'AsSingleQuery()' globally avoids the error but may cause cartesian explosion and slow queries. (70% 失败率)