Question

我收到以下错误：

无法创建常量值类型 'Phoenix.Intranet.Web.ClientSettings.ComponentRole'。只有原始类型（'如Int32，支持String和Guid'）这个背景。

我理解错误发生的原因。我不明白的是我的代码创建错误的原因。我的比较是针对原始类型的。所有的比较都是Guid to Guid。该错误明确指出Guids没问题。

此行发生错误（向下）：

 var vla =  (from cir in phoenixEntities.ComponentInRoles

代码：

List<ComponentRole> roles;
using (IMSMembershipEntities entities = new IMSMembershipEntities())
{
    roles = (from role1 in entities.Roles
             select new ComponentRole{Name = role1.RoleName, RoleId = role1.RoleId} ).ToList();
}

List<Components> componentInRoles;

using (PhoenixEntities phoenixEntities = new PhoenixEntities())
{
    phoenixEntities.ContextOptions.LazyLoadingEnabled = false;
    componentInRoles = (from component in phoenixEntities.Components
                        select new Components{Name = component.Name,
                                              ComponentId = component.ComponentId,
                                              //InRoles = (from componentInRole in phoenixEntities.ComponentInRoles
                                              //           join role in roles on componentInRole.RoleId equals role.RoleId 
                                              //           where componentInRole.ComponentId == component.ComponentId
                                              //           select new ComponentRole{RoleId = role.RoleId, Name = role.Name})
                                              }
                       ).ToList();


    foreach (Components cmpent in componentInRoles)
    {
        Components cmpent1 = cmpent;
        //cmpent.InRoles = 

         var vla =  (from cir in phoenixEntities.ComponentInRoles
                     join role in roles on cir.RoleId equals role.RoleId
                     where cir.ComponentId == cmpent1.ComponentId
                         select role).ToList();
    }
}

Answer 1

EntityFramework和Linq to SQL都试图将部分在内存中而另一部分在数据库中的此类查询转换为sql IN运算符。

并且因为你的类哪个角色是IEnumerable而不是原始类型，所以它无法转换为SQL查询。

首先应该从数据库获取到内存，然后在内存中加入两个列表。

例如：

 var vla =  (from cir in phoenixEntities.ComponentInRoles.ToList()
                     join role in roles on cir.RoleId equals role.RoleId
                     where cir.ComponentId == cmpent1.ComponentId
                         select role).ToList();

我希望我帮助

在此上下文中仅支持原始类型（例如Int32，String和Guid'）

1 个答案: