Question

我想通过userId

查找用户名

此代码段工作

Discussion_CreateBy = db.AspNetUsers.Find(discussion.CreatedBy).UserName,

这一次不适用于以下控制器类

Comment_CreateBy = db.AspNetUsers.Find(c.CreatedBy).UserName,

这是我的模型类

public class DiscussionVM
{
    public int Disussion_ID { get; set; }
    public string Discussion_Title { get; set; }
    public string Discussion_Description { get; set; }
    public Nullable<System.DateTime> Discussion_CreateDate { get; set; }
    public string Discussion_CreateBy { get; set; }

    public string Comment_User { get; set; }

    public IEnumerable<CommentVM> Comments { get; set; }

}

public class CommentVM
{

    public int Comment_ID { get; set; }
    public Nullable<System.DateTime> 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

方法＆＃39; Project.Models.AspNetUser Find（System.Object []）＆＃39;声明类型＆＃39; System.Data.Entity.DbSet 1[Project.Models.AspNetUser]' cannot be called with instance of type 'System.Data.Entity.Core.Objects.ObjectQuery 1 [Project.Models.AspNetUser]＆＃39;

Answer 1

Discussion_CreateBy = db.AspNetUsers.Find(discussion.CreatedBy).UserName

可行，因为讨论是一个内存中对象，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尚未查询，因为

db.AB_DiscussionComments.Where(c => c.Discussion_ID == Discussion_ID)

返回IQueriable而不是实际的评论集合

解决问题的最简单方法是将所有评论都记录在内存中（因为无论如何都需要它们）：

var comments = db.AB_DiscussionComments.Where(c => c.Discussion_ID == Discussion_ID).ToList();

不能使用类型＆System; System.Data.Entity.Core.Objects.ObjectQuery

1 个答案: