我遇到性能问题但不了解EF的行为。我使用ASP.NET MVC应用程序,并在模型中包含以下代码:
public List<Portal> PortalListWithCategories()
{
List<Portal> q = new List<Portal>();
q = (from i in _dataContext.Portals.Include("Categories").Include("Ideas") where i.Categories.Count > 0 orderby i.DefaultPortal descending select i).ToList();
return q;
}
我从控制器调用它:
portalList = _repository.PortalListWithCategories();
据我所知,EF应该执行批量请求并返回具有嵌套集合“Categories”和“Ideas”的门户集合。
但是我看到了以下内容:
@foreach (var category in portal.Categories.Where(n => n.Ideas.Count > 0 && n.Portals.Any(g => g.PortalID == portal.PortalID)))
{
if ((from e in category.Ideas where e.Portals.Any(t => t.PortalID == portal.PortalID) select e).Count() > 0)
{
string categoryLink = Url.RouteUrl("Full", new { PortalID = portal.PortalID, CategoryID = category.CategoryID, action = "Ideas" });
List<NEOGOV_Ideas.Models.Ideas> ideas = category.Ideas.Where(o => o.Portals.Any(p => p.PortalID == portal.PortalID) && o.Categories.Any(h => h.CategoryID == category.CategoryID)).OrderByDescending(k => k.CreatedDateTime).ToList();
<div class="grid_4">
<h4>
<a href="@categoryLink">@category.CategoryName<span class="count_link"> (@ideas.Count())</span>
<span class="follow_link">»</span></a></h4>
<ul>
@foreach (var idea in ideas.Take(3))
{
string ideaLink = Url.RouteUrl("IdeaShort", new { id = idea.IdeaID });
if (!idea.IdeaTypeReference.IsLoaded) { idea.IdeaTypeReference.Load(); }
string cssclass = " class=\"" + idea.IdeaType.TypeName.ToLower() + "\"";
<li><a href="@ideaLink" @cssclass>@idea.Title</a></li>
}
</ul>
</div>
if (i == 2)
{
<div class="clear">
</div>
}
i++;
}
}
据我所知,我不应该对DB有新的请求,但我有很多。为什么呢?
[ADDED]
我找到了这个字符串 (来自e in category.Ideas,其中e.Portals.Any(t =&gt; t.PortalID == portal.PortalID)选择e).Count() 向DB生成许多请求,如:exec sp_executesql N'SELECT [Extent2]。[PortalID] AS [PortalID], [Extent2]。[PortalName] AS [PortalName], [Extent2]。[DefaultPortal] AS [DefaultPortal] FROM [dbo]。[PortalIdeas] AS [Extent1] INNER JOIN [dbo]。[门户] AS [Extent2] ON [Extent1]。[PortalID] = [Extent2]。[PortalID] WHERE [Extent1]。[IdeaID] = @ EntityKeyValue1',N'@ EntityKeyValue1 int',@ EntityKeyValue1 = 5618
为什么它会发生在Count()?
第二个问题如何正确使用?
答案 0 :(得分:1)
由于e.Portals
未加载并且在foreach
循环中,因此EF必须往返数据库以获取Idea的Portals
。
您也应该在查询中包含Ideas
。
我没有对此进行测试,但我认为您应该添加.Include("Ideas.Portals")
(或者如果您使用EF 4.1,请添加using System.Data.Entity
并使用.Include(c => c.Ideas.Portals)
)。