操作无法完成，因为 DbContext 已被处理错误

问题描述

我是 EF 的新手，我正在尝试使用一种扩展方法，该方法将我的数据库类型 User 转换为我的信息类 UserInfo.
如果有区别，我会先使用数据库吗?

I'm new to EF and I'm trying to use an extension method which converts from my Database type User to my info class UserInfo.
I'm using database first if that makes a difference?

我下面的代码给出了错误

My code below gives the error

操作无法完成，因为 DbContext 已被释放.

try
{
    IQueryable<User> users;
    using (var dataContext = new dataContext())
    {
        users = dataContext.Users
                  .Where(x => x.AccountID == accountId && x.IsAdmin == false);
        if(users.Any() == false)
        {
            return null;
        }
    }
    return users.Select(x => x.ToInfo()).ToList(); // this line is the problem
}
catch (Exception ex)
{
    //...
}

我明白为什么会这样做，但我也不明白为什么 where 语句的结果没有保存到 users 对象中?

I can see why it would do it, but I also don't understand why the result of the where statement isn't being saved into the users object?

所以我想我的主要问题是为什么它不起作用，其次使用扩展方法和 EF 的正确方法是什么?

So I guess my main question is why doesn't it work and secondly what's the right way of using extension methods and EF?

推荐答案

这个问题&answer 让我相信 IQueryable 需要一个活动上下文来进行操作.这意味着你应该试试这个:

This question & answer lead me to believe that IQueryable require an active context for its operation. That means you should try this instead:

try
{
    IQueryable<User> users;

    using (var dataContext = new dataContext())
    {
        users = dataContext.Users.Where(x => x.AccountID == accountId && x.IsAdmin == false);

        if(users.Any() == false)
        {
            return null;
        }
        else
        {
            return users.Select(x => x.ToInfo()).ToList(); // this line is the problem
        }
    }


}
catch (Exception ex)
{
    ...
}

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