C# ASP.NET Core Web API 包含在哪里

Question

我有这样的代码：

public Blog GetBlogWithCategoryTagsAndCommentsWithReplies(int id)
    {
        return _context.Blogs
            .Where(blog => blog.Id == id)
            .Include(blog => blog.Category)
            .Include(blog => blog.BlogTags)
                .ThenInclude(blogtag => blogtag.Tag)
            .Include(blog => blog.Comments)
                .ThenInclude(comment => comment.User)
            .Include(blog => blog.Comments)
                .ThenInclude(comment => comment.Replies)
                    .ThenInclude(reply => reply.User)
            .FirstOrDefault();
    }

在此状态下工作没有任何问题。

但是当我在我的代码中添加 where 时，当我把它写成

public Blog GetBlogWithCategoryTagsAndCommentsWithReplies(int id)
    {
        return _context.Blogs
            .Where(blog => blog.Id == id)
            .Include(blog => blog.Category)
            .Include(blog => blog.BlogTags)
                .ThenInclude(blogtag => blogtag.Tag)
            .Include(blog => blog.Comments.Where(comment=>comment.Confirmation==true))
                .ThenInclude(comment => comment.User)
            .Include(blog => blog.Comments)
                .ThenInclude(comment => comment.Replies.Where(reply=>reply.Confirmation==true))
                    .ThenInclude(reply => reply.User)
            .FirstOrDefault();
    }

所以当我询问评论并回复 return confirmation == true 时，我收到以下错误。

错误：Include 中使用的 Lambda 表达式无效。

我该如何解决这个问题？

Answer 1

您应该将属性名称作为字符串传递。

喜欢 .Include("类别")

您可以在此处查看该方法的重载：https://docs.microsoft.com/en-us/dotnet/api/system.data.objects.objectquery-1.include?view=netframework-4.8

Answer 2

恐怕 filtered include 仅受 EF Core v5.0.0 的支持，目前在 preview 中。

如果您使用的是较旧的 EF Core 版本，您可以查看 this thread 中的一些想法。

例如，如果您能承受在内存中提取所有内容和过滤的性能影响，您可以尝试执行以下操作：

var blog = _context.Blogs
   .Where(blog => blog.Id == id)
   .Include(blog => blog.Category)
   .Include(blog => blog.BlogTags)
      .ThenInclude(blogtag => blogtag.Tag)
   .Include(blog => blog.Comments)
      .ThenInclude(comment => comment.User)
   .Include(blog => blog.Comments)
      .ThenInclude(comment => comment.Replies)
         .ThenInclude(reply => reply.User)
   .FirstOrDefault();

blog.Comments = blog.Comments.Where(comment => comment.Confirmation == true).ToList();

foreach(var comment in blog.Comments)
{
   comment.Replies = comment.Replies.Where(reply => reply.Confirmation == true).ToList();
}

return blog;

C# ASP.NET Core Web API 包含在哪里

C# ASP.NET Core Web API include with where

c#

linq-to-entities

entity-framework-core

.net-core