如何在泛型UnitOfWork类中正确使用ThenInclude方法？

当前你的FindByConditionAsync方法通过params Expression<Func<TEntity, object>>[] includes参数处理关联数据加载，但这种方式仅支持添加一级导航属性的Include，无法实现ThenInclude的链式导航加载——因为ThenInclude依赖前一个Include返回的导航属性上下文，数组形式的参数无法传递这种链式依赖关系。

解决方案：改用委托构建查询链 #

修改方法，将includes参数替换为Func<IQueryable<TEntity>, IQueryable<TEntity>>类型的委托，让调用者自行构建包含Include和ThenInclude的完整查询逻辑。这种方式灵活性极强，还能支持其他查询配置（如AsNoTracking）。

修改后的代码

public async Task<IEnumerable<TEntity>> FindByConditionAsync(
    Expression<Func<TEntity, bool>> filter = null,
    Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
    Func<IQueryable<TEntity>, IQueryable<TEntity>> includeBuilder = null)
{
    IQueryable<TEntity> query = dbSet;

    // 处理关联加载（支持Include+ThenInclude链式调用）
    if (includeBuilder != null)
    {
        query = includeBuilder(query);
    }

    if (filter != null)
    {
        query = query.Where(filter);
    }

    if (orderBy != null)
    {
        query = orderBy(query);
    }

    return await query.ToListAsync();
}

调用示例

调用时直接在includeBuilder委托里链式编写Include和ThenInclude：

var result = await yourRepository.FindByConditionAsync(
    filter: e => e.Id == 1,
    includeBuilder: q => q.Include(e => e.OrderItems)
                          .ThenInclude(oi => oi.Product)
                          .Include(e => e.Customer)
);

兼容原有调用的可选方案 #

如果需要保留原有includes参数的调用方式，可以重载方法，同时兼容新旧逻辑：

// 原有方法，兼容旧调用
public async Task<IEnumerable<TEntity>> FindByConditionAsync(
    Expression<Func<TEntity, bool>> filter = null,
    Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
    params Expression<Func<TEntity, object>>[] includes)
{
    return await FindByConditionAsync(
        filter,
        orderBy,
        q => includes.Aggregate(q, (current, include) => current.Include(include))
    );
}

// 新增的支持ThenInclude的方法
public async Task<IEnumerable<TEntity>> FindByConditionAsync(
    Expression<Func<TEntity, bool>> filter = null,
    Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
    Func<IQueryable<TEntity>, IQueryable<TEntity>> includeBuilder = null)
{
    IQueryable<TEntity> query = dbSet;

    if (includeBuilder != null)
    {
        query = includeBuilder(query);
    }

    if (filter != null)
    {
        query = query.Where(filter);
    }

    if (orderBy != null)
    {
        query = orderBy(query);
    }

    return await query.ToListAsync();
}

内容的提问来源于stack exchange，提问作者mamad2559