asp.net-mvc – 实体框架 – 无法创建x类型的常量值.在此上下文中仅支持基元类型.

我有以下内容

工程师模型：

public class engineers
{
    public Guid? Guid { get; set; }
    public string Name { get; set; }
}

我在工程师名单中填写正确的详细信息：

List<engineers> listeng = new List<engineers>();
listeng.Add(new engineers { Name = profile.FirstName + " " + profile.LastName,Guid = GuidEngineer });

到现在为止还挺好.

我的问题如何将工程师名称拉到下面的eng条目：

var tickets = from o in new HelpdeskEntities().Tickets.Where(t => t.TicketState.State == "Open")
                    select new AjaxTickets
                    {
                        TicketID = o.TicketID,TicketSubject = o.TicketSubject,ClientCompanyName = o.ClientCompany.ClientCompanyName,DateOpened = o.DateOpened,**eng** = list.Where(x => x.Guid == o.EngineerID).Select(x => new engineers {Guid = x.Guid,Name=x.Name }).FirstOrDefault().Name

                    };

我也试过了

var tickets = from o in new HelpdeskEntities().Tickets.Where(t => t.TicketState.State == "Open")
                    select new AjaxTickets
                    {
                        TicketID = o.TicketID,**eng** = list.Where(x => x.Guid == o.EngineerID).Select(x => x.Name }).FirstOrDefault()
                    };

我得到的错误是：

Unable to create a constant value of type 'Helpdesk2.viewmodel.engineers'. Only primitive types ('such as Int32,String,and Guid') are supported in this context."}

我有点理解,但不能弄清楚只是为了选择工程师的名字.

提前致谢

解决方法

您应该能够简化第一个：

list.FirstOrDefault(x => x.Guid == o.EngineerID).Name

话虽如此,实体框架可能不会让你在运行数据库调用时运行它.如果您可以从票证到工程师创建外键,则可以按照与客户公司名称相同的方式进行选择.如果没有,那么你需要在两个方面做到这一点：首先,运行select而不填充工程师名称属性,然后用以下内容填充它们：

tickets.ForEach(ticket => ticket.EngineerName = engineers.First(eng => eng.Guid == ticket.EngineerID).Name)

显然,您需要添加EngineerID属性并在第一步中选择它.