Question

我使用以下代码：

using(MainEntities mainContext = new MainEntities())
{
    return (from member in mainContext.aspnet_Membership
            where adminGroupUserIDs.Contains(member.UserId)
            select new
            {
                FullName = member.FirstName + " " + member.LastName,
                UserName = (from user in mainContext.aspnet_Users
                            where user.UserId == member.UserId
                            select user.UserName)
            }).ToList(); 
}

其中adminGroupUserIDs是IQueryable<GUID>，是根据查询形成MainEntities的其他实例。

有了这个查询，LINQ抱怨说：

指定的LINQ表达式包含对与不同上下文关联的查询的引用。

任何想法为什么？

Answer 1

我无法从您在此处显示的代码中确定，但我非常确定adminGroupUserIDs是另一个尚未检索到的查询的结果，并且是使用不同的实例创建的MainEntities。您不能混合来自不同上下文的查询，甚至不能混合相同上下文类的不同实例。尝试将其更改为以下内容：

var loadedAdminGroupUserIDs = adminGroupUserID.ToArray();

using(MainEntities mainContext = new MainEntities())
{
    return (from member in mainContext.aspnet_Membership
            where loadedAdminGroupUserIDs.Contains(member.UserId)
            select new
            {
                FullName = member.FirstName + " " + member.LastName,
                UserName = (from user in mainContext.aspnet_Users
                            where user.UserId == member.UserId
                            select user.UserName)
            }).ToList(); 
}

Answer 2

尝试将.FirstOrDefault()添加到子查询中。

using(MainEntities mainContext = new MainEntities())
{
    return (from member in mainContext.aspnet_Membership
            where adminGroupUserIDs.Contains(member.UserId)
            select new
            {
                FullName = member.FirstName + " " + member.LastName,
                UserName = (from user in mainContext.aspnet_Users
                            where user.UserId == member.UserId
                            select user.UserName).FirstOrDefault()
            }).ToList(); 
}

一个上下文引用LINQ查询抛出多个引用异常 - BUG？

2 个答案: