过滤实体框架中的包含项答案

【问题标题】：Filtering include items in Entity Framework过滤实体框架中的包含项
【发布时间】：2017-07-20 18:11:51
【问题描述】：

我已经阅读了这个post，并且我已经在 EntityFramework 核心中实现了一个 linq 查询。这是c#语法：

    DateTime today = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day);
    var actionMenuGroup = Context.ActionMenuGroups
                  .Include(am => am.ActionMenus)
                  .Where(am => am.ActionMenus.Any(amm => amm.DeliveryDate.GetValueOrDefault(DateTime.MinValue).CompareTo(today) <= 0 && amm.AuthorizedCustomers.Any(ac => ac.CustomerId.Equals(CustomerId) && ac.DeliveryDate.GetValueOrDefault(DateTime.MinValue).CompareTo(today)<=0)))
                  .Select(g => new ActionMenuGroup()
                  {
                      Id = g.Id,
                      Name = g.Name,
                      SortOrder = g.SortOrder,
                      ActionMenus = g.ActionMenus.Where(amm => amm.DeliveryDate.GetValueOrDefault(DateTime.MinValue).CompareTo(today) <= 0 && amm.AuthorizedCustomers.Any(ac => ac.CustomerId.Equals(CustomerId) && ac.DeliveryDate.GetValueOrDefault(DateTime.MinValue).CompareTo(today) <= 0)).ToList()
                  });

一切正常！但是，在插入 lambda 过滤器表达式后，选择出错了；这是带有 lambda 的新版本：

public Func<Model.ActionMenu, DateTime, int?, bool> filterActionMenu = (amm, oggi, CustomerId) => amm.DeliveryDate.GetValueOrDefault(DateTime.MinValue).CompareTo(oggi) <= 0 && amm.AuthorizedCustomers.Any(ac => ac.CustomerId.Equals(CustomerId) && ac.DeliveryDate.GetValueOrDefault(DateTime.MinValue).CompareTo(oggi) <= 0);

    public IQueryable<ActionMenuGroup> GetActionMenuAndMenuGroupByCustomer(int? CustomerId)
    {
        DateTime today = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day);
        var actionMenuGroup = Context.ActionMenuGroups
                  .Include(am => am.ActionMenus)
                  .Where(am => am.ActionMenus.Any(amm => filterActionMenu(amm,today, CustomerId)))
                  .Select(g => new ActionMenuGroup()
                  {
                      Id = g.Id,
                      Name = g.Name,
                      SortOrder = g.SortOrder,
                      ActionMenus = g.ActionMenus.Where(amm => filterActionMenu(amm, today, CustomerId)).ToList()
                  });
        return actionMenuGroup;
    }

有没有人有在 linq 语法中使用 lambda 的经验？谢谢

【问题讨论】：

标签： linq lambda include

【解决方案1】：

试试：

public Expression<Func<Model.ActionMenu, DateTime, int?, bool>>  filterActionMenu = (amm, oggi, CustomerId) => ....

【讨论】：

James，以及在 ICollection<T> 类型的导航属性的表达式树中如何在语法上使用它？