[英]Error in Json Serialization “There is already an open DataReader associated with this Command”
Json序列化命令給出了此錯誤。 我使用Newtonsoft.Json
來避免序列化時的循環引用錯誤。
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
給出了錯誤。
我可以使用MultipleActiveResultSets=True;
來解決它MultipleActiveResultSets=True;
但是我在哪里進行第二次查詢?
公開ActionResult GetStudies(int pageSize = 10,int pageNum = 1){var Studies = GetStudiesData()。ToList(); //解決,創建了另一個問題//其他代碼}
現在,返回的Json看起來像是再次將Json序列化為字符串。
"{\"TotalRows\":5,\"Rows\":[{\"AssignedUser\":null, ..... }]}"
當由javascript解析時,它們全部拆分為一個字符數組。
變
//data is a json string after serialization
return Json(data, JsonRequestBehavior.AllowGet); //Serializing the Json
至
return Content(data, "application/json");
將其分配給列表,然后對其進行查詢應避免這種情況:
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);
您對此處的DbSet<Studies>
有兩個查詢
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