[英]Error in Json Serialization “There is already an open DataReader associated with this Command”
Json序列化命令给出了此错误。 我使用Newtonsoft.Json
来避免序列化时的循环引用错误。
private IQueryable<Study> GetStudiesData()
{
var currUser = UserManager.FindById(User.Identity.GetUserId());
var currUserRole = currUser.Roles.First();
IQueryable<Study> studies;
if (User.IsInRole("SuperAdmin")) {
studies = db.Studies; //all studies from all centers
}
else {
var assignedStudies = db.Studies.Where(s => s.AssignedUserID == currUser.Id);
studies = db.Studies.Where(s => s.User.CenterId == currUser.CenterId && s.RoleID == currUserRole.RoleId)
.Concat(assignedStudies);
}
return studies;
}
//ajax call to this function gives error
public ActionResult GetStudies(int pageSize = 10, int pageNum = 1)
{
var studies = GetStudiesData();
var studiesCount = studies.Count();
var studiesPaged = studies.OrderBy(s=>s.PatientID).Skip(pageSize*pageNum).Take(pageSize);
var result = new { TotalRows = studiesCount, Rows = studiesPaged };
//this line gives error
//There is already an open DataReader associated with this Command which must be closed first.
var data = Newtonsoft.Json.JsonConvert.SerializeObject(result, Newtonsoft.Json.Formatting.None,
new Newtonsoft.Json.JsonSerializerSettings()
{
ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
});
return Json(data, JsonRequestBehavior.AllowGet);
}
我想result = studies
, result = studiesPaged
, result = studiesCount
在var data = Newtonsoft.Json.JsonConvert.SerializeObject(result, ...)
只有studiesPaged
给出了错误。
我可以使用MultipleActiveResultSets=True;
来解决它MultipleActiveResultSets=True;
但是我在哪里进行第二次查询?
公开ActionResult GetStudies(int pageSize = 10,int pageNum = 1){var Studies = GetStudiesData()。ToList(); //解决,创建了另一个问题//其他代码}
现在,返回的Json看起来像是再次将Json序列化为字符串。
"{\"TotalRows\":5,\"Rows\":[{\"AssignedUser\":null, ..... }]}"
当由javascript解析时,它们全部拆分为一个字符数组。
变
//data is a json string after serialization
return Json(data, JsonRequestBehavior.AllowGet); //Serializing the Json
至
return Content(data, "application/json");
将其分配给列表,然后对其进行查询应避免这种情况:
public ActionResult GetStudies(int pageSize = 10, int pageNum = 1)
{
var studies = GetStudiesData().ToList();
var studiesCount = studies.Count();
var studiesPaged = studies.OrderBy(s=>s.PatientID).Skip(pageSize*pageNum).Take(pageSize);
var result = new { TotalRows = studiesCount, Rows = studiesPaged };
//this line gives error
//There is already an open DataReader associated with this Command which must be closed first.
var data = Newtonsoft.Json.JsonConvert.SerializeObject(result, Newtonsoft.Json.Formatting.None,
new Newtonsoft.Json.JsonSerializerSettings()
{
ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
});
return Json(data, JsonRequestBehavior.AllowGet);
}
var assignedStudies = db.Studies.Where(s => s.AssignedUserID == currUser.Id);
studies = db.Studies.Where(s => s.User.CenterId == currUser.CenterId &&
s.RoleID == currUserRole.RoleId).Concat(assignedStudies);
您对此处的DbSet<Studies>
有两个查询
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