在此上下文中仅支持原始类型(例如Int32,String和Guid')

Question

我收到以下错误:

无法创建类型为"Phoenix.Intranet.Web.ClientSettings.ComponentRole"的常量值.在此上下文中仅支持原始类型(例如Int32,String和Guid').

我理解为什么会出错.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是可以的.

此行发生错误(朝向底部):

 var vla =  (from cir in phoenixEntities.ComponentInRoles

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都试图将一部分在内存中而另一部分在数据库中的查询转换为sql IN运算符.

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

您应首先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();

我希望我帮忙