Question

在＆＃34;每个＆＃34;，当运行＆＃34; FirstOrDefault＆＃34;将出现错误＆＃34;已经存在与此Connection关联的打开的DataReader，必须先关闭它。＆＃34;。怎么办？

public int SetUser(string[] dIds, string pId)
{
    using (var scope = _dbContextScopeFactory.Create())
    {
        var db = scope.DbContexts.Get<JuCheapContext>();

        var users = db.Users;

        var user = users.FirstOrDefault(m => m.Id == pId);
        if (user.Places == null)
        {
            user.Places = new List<PlaceEntity>();
        }

        var place = db.Place.Include(m => m.User).Where(m => dIds.Contains(m.Id));

        place.Each(m =>
        {
            user.Places.Add(m);

            //There is already an open DataReader associated with this Connection which must be closed first.
            var pu = users.FirstOrDefault(u => u.LoginName == m.Key);

            if (pu != null)
            {
                pu.FId = pId;
            }

        });

        return db.SaveChanges();
    }
}

Answer 1

当你说

时

place.Each(m =>

您正在使用阅读器来迭代数据库中的项目

然后

  var pu = users.FirstOrDefault(u => u.LoginName == m.Key);

第二个读取器在第一个读取器仍在执行时进入，并且发生错误

调用ToList（）将数据存入内存并关闭阅读器

var place = db.Place.Include(m => m.User).Where(m => dIds.Contains(m.Id)).ToList();

您还可以启用MARS（多个活动结果集）

https://msdn.microsoft.com/en-us/library/h32h3abf(v=vs.110).aspx

实体框架，已经有一个与此Connection关联的开放DataReader，必须先关闭它

1 个答案: