不能使用’System.Data.Entity.Core.Objects.ObjectQuery类型的实例调用
我想通过userId查找用户名
这段代码片段正常工作
Discussion_CreateBy = db.AspNetUsers.Find(discussion.CreatedBy).UserName, 这曾经不适用于以下控制器类
Comment_CreateBy = db.AspNetUsers.Find(c.CreatedBy).UserName,
这是我的模特课
public class DiscussionVM { public int Disussion_ID { get; set; } public string Discussion_Title { get; set; } public string Discussion_Description { get; set; } public Nullable Discussion_CreateDate { get; set; } public string Discussion_CreateBy { get; set; } public string Comment_User { get; set; } public IEnumerable Comments { get; set; } } public class CommentVM { public int Comment_ID { get; set; } public Nullable Comment_CreateDate { get; set; } public string Comment_CreateBy { get; set; } public string Comment_Description { get; set; } }
这是整个控制器类
public ActionResult Discussion_Preview() { int Discussion_ID = 1; var discussion = db.AB_Discussion.Where(d => d.Discussion_ID == Discussion_ID).FirstOrDefault(); var comments = db.AB_DiscussionComments.Where(c => c.Discussion_ID == Discussion_ID); DiscussionVM model = new DiscussionVM() { Disussion_ID = discussion.Discussion_ID, Discussion_Title = discussion.Discussion_Name, Discussion_Description = discussion.Discussion_Name, Discussion_CreateBy = db.AspNetUsers.Find(discussion.CreatedBy).UserName, Discussion_CreateDate = discussion.CreatedDate, Comments = comments.Select(c => new CommentVM() { Comment_ID = c.Comment_ID, Comment_Description = c.Comment_Discription, Comment_CreateBy = db.AspNetUsers.Find(c.CreatedBy).UserName, Comment_CreateDate = c.CreatedDate }) }; return View(model); }
获得以下错误
1[Project.Models.AspNetUser]' cannot be called with instance of type 'System.Data.Entity.Core.Objects.ObjectQuery在类型’System.Data.Entity.DbSet1[Project.Models.AspNetUser]' cannot be called with instance of type 'System.Data.Entity.Core.Objects.ObjectQuery上声明的方法’Project.Models.AspNetUser Find（System.Object []）’1[Project.Models.AspNetUser]' cannot be called with instance of type 'System.Data.Entity.Core.Objects.ObjectQuery1 [Project.Models.AspNetUser]’
Discussion_CreateBy = db.AspNetUsers.Find(discussion.CreatedBy).UserName
之所以有效是因为讨论是内存中的对象，因为您通过调用FirstOrDefault来执行查询：
var discussion = db.AB_Discussion.Where(d => d.Discussion_ID == Discussion_ID).FirstOrDefault();
另一方面，在以下声明中：
db.AspNetUsers.Find(c.CreatedBy).UserName
c尚未被查询，因为
db.AB_DiscussionComments.Where(c => c.Discussion_ID == Discussion_ID)
返回IQueriable而不是实际的注释集合
解决它的最简单方法是将所有注释带入内存（因为你无论如何都需要它们）：
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var comments = db.AB_DiscussionComments.Where(c => c.Discussion_ID == Discussion_ID).ToList();
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