查找数据从第二个数据库从关键在第一个数据库asp.net mvc

本文关键字：数据库 asp 第一个 net mvc 数据 第二个 查找 | 更新日期: 2023-09-27 18:14:55

在控制器中为列表运行get方法时出现以下错误:

指定的LINQ表达式包含对与不同上下文关联的查询的引用。

调试完控制器后，order语句产生了错误

方法是:

    public ActionResult OwnerList()
    {                              
        var owners = (from s in db.Owners                       
                     orderby Peopledb.Posts.FirstOrDefault(x => x.PostId == s.PostId).PostName
                     select s).ToList();
        var viewModel = owners.Select(t => new OwnerListViewModel
        {
             Created = t.Created,
             PostName = Peopledb.Posts.FirstOrDefault(x => x.PostId == t.PostId).PostName,
             Dormant = t.Dormant,
             OwnerId = t.OwnerId,
        });
        return PartialView("_OwnerList", viewModel);
    }

第一个数据库中Owner的Class是，dbcontext = IARContext:

public class Owner
{
    public int OwnerId { get; set; }
    [Column(TypeName = "int")]
    public int PostId { get; set; }
    [Column(TypeName = "bit")]
    public bool Dormant { get; set; }
    [Column(TypeName = "datetime2")]
    public DateTime Created { get; set; }
    public virtual ICollection<Asset> Assets { get; set; }
    public People.Models.Post Post { get; set; }
}

第二个数据库中的Post类为:dbcontext = PeopleContext:

public class Post
{
    public int PostId { get; set; }
    [StringLength(50)]
    [Column(TypeName = "nvarchar")]
    public string PostName { get; set; }
    [Column(TypeName = "bit")]
    public bool Dormant { get; set; }
    [StringLength(350)]
    [Column(TypeName = "nvarchar")]
    public string Description { get; set; }
    public virtual ICollection<Contract> Contracts { get; set; }
    public virtual ICollection<Owner> Owners { get; set; }
}

我试图查找PostName从Post在人数据库当显示从IAR数据库的所有者列表

查找数据从第二个数据库从关键在第一个数据库asp.net mvc

对我来说，信息很清楚:你正在混合两种上下文。这不可能。这几乎意味着创建一个临时dblinq。

解决方案如下:

  • 全局上下文
  • 按代码分隔(如果上下文不能全球化):

对我来说你应该有

public ActionResult OwnerList()
{                              
    var owners = (from s in db.Owners                                   
                 //can't order from here without a dbling/global context
                 select s);
    //may be a where is missing here ?
    List<DAOSomeName> viewModel = owners.Select(t => new DAOSomeName
    {
         Created = t.Created,             
         Dormant = t.Dormant,
         OwnerId = t.OwnerId,
    });// .ToList(); the materialization is done by the following foreach
    //until here, no run to the db, no data transfered.
    foreach (DAOSomeName m in viewModel ) {
        m.PostName = Peopledb.Posts.Where(x => x.PostId == t.PostId).
            Select(x => x.PostName).FirstOrDefault();
        //this way you also handle the null case pointed by Trevor
    }
    //please note that this way, yout view model is not anymore linked
    //to the context, except if one property is a navigation property
    return PartialView("_OwnerList", viewModel.OrderBy(x => x.PostName));
}
public class DAOSomeName {
    public DateTime Created {get; set;}
    //Dormant, OwnerId, PostName...
}

通过修改我的控制器:

    public ActionResult OwnerList()
    {
        var posts = new List<People.Models.Post>(Peopledb.Posts);
        var owners = new List<Owner>(db.Owners);
        var ownerposts = (from c in posts
                         join d in owners on c.PostId equals d.PostId
                         orderby c.PostName
                         select new OwnerPost { OwnerId = d.OwnerId, PostName = c.PostName, Created = d.Created, Dormant = d.Dormant }).ToList();
        var viewModel = ownerposts.Select(t => new OwnerListViewModel
        {
            Created = t.Created,
            PostName = t.PostName,
            Dormant = t.Dormant,
            OwnerId = t.OwnerId,
        });
        return PartialView("_OwnerList", viewModel);
    }

和添加OwnerPost类:

public class OwnerPost
{
    public int OwnerId { get; set; }
    public string PostName { get; set; }
    public bool Dormant { get; set; }
    public DateTime Created { get; set; }
}

我解决了这个问题

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