Error 'cannot be initialized in a query result' when trying to get data with Linq - asp.net-mvc

Question

ISSUE:
I have an asp.net mvc 3 app. I'm using EF 4.1 and trying out jqGrid. I'm trying to get data for my jqGrid using the GridData method below. I get the following error on the group of data starting at 'var jsonData = new...'. Any ideas?
ERROR:
{"The array type 'System.String[]' cannot be initialized in a query result.
Consider using 'System.Collections.Generic.List`1[System.String]' instead."}
GridData Method:
public JsonResult GridData(string sidx, string sord, int page, int rows)
{
var result = from a in db.t_harvest_statistics_elk
where a.year == "2008" && a.unit_number == 1
orderby a.id
select a;
int pageIndex = Convert.ToInt32(page) - 1;
int pageSize = rows;
int totalRecords = result.Count(); // context.Questions.Count();
int totalPages = (int)Math.Ceiling((float)totalRecords / (float)pageSize);
var questions = result.Skip(pageIndex * pageSize).Take(pageSize);
var jsonData = new
{
total = totalPages,
page,
records = totalRecords,
rows = (
from question in questions
select new
{
i = question.id,
cell = new string[] { SqlFunctions.StringConvert((double)question.id), SqlFunctions.StringConvert((double)question.total_rec_days), question.year }
}).ToArray()
};
return Json(jsonData);
}
HERE IS AN EXAMPLE THAT DOES WORK
public JsonResult DynamicGridData(string sidx, string sord, int page, int rows)
{
var context = new HaackOverflowDataContext();
int pageIndex = Convert.ToInt32(page) - 1;
int pageSize = rows;
int totalRecords = context.Questions.Count();
int totalPages = (int)Math.Ceiling((float)totalRecords / (float)pageSize);
var questions = context.Questions.OrderBy(sidx + " " + sord).Skip(pageIndex * pageSize).Take(pageSize);
var jsonData = new
{
total = totalPages,
page,
records = totalRecords,
rows = (
from question in questions
select new
{
i = question.Id,
cell = new string[] { question.Id.ToString(), question.Votes.ToString(), question.Title }
}).ToArray()
};
return Json(jsonData);
}

Answer 1

The easiest way to fix the code will be to use something like the following
// to be able to use ToString() below which is NOT exist in the LINQ to Entity
// so we should get the data from the database and save the result locally before
// the next step. One can use .ToList() or to .AsEnumerable(), but one should
// choose only the fields of questions which we will need later
var queryDetails = (from item in questions
select new { item.id, item.total_rec_days, item.year }).ToList();
var jsonData = new {
total = totalPages,
page,
records = totalRecords,
rows = (
from question in queryDetails
select new
{
id = question.Id,
cell = new [] {
question.Id.ToString(),
question.total_rec_days.ToString(),
question.year.ToString()
}
}).ToArray()
};
return Json(jsonData, JsonRequestBehavior.AllowGet);
Your current code contain some small problems like the usage of i = question.id instead of id = question.id.
I would recommend you to read the answer and download the demo from the answer which contains more recent and extended code.

Answer 2

var jsonData = new {
total = totalPages,
page,
records = totalRecords,
rows = (
from question in queryDetails
select new
{
id = question.Id,
cell = new IComparable[]{
question.Id.ToString(),
question.total_rec_days.ToString(),
question.year.ToString()
}
}).ToArray()
};
return Json(jsonData, JsonRequestBehavior.AllowGet);

Answer 3

Can you try modifying your code like :
rows = (
from question in questions.AsEnumerable() //AsEnumerable() is added to switch to LINQ to Entites to eager load the data.
select new
{
i = question.id,
cell = new string[] { SqlFunctions.StringConvert((double)question.id), SqlFunctions.StringConvert((double)question.total_rec_days), question.year }
}).ToArray()
Because the MSDN says that : "You cannot call this function directly. This function can only appear within a LINQ to Entities query." (Though the next line is little confusing in documentation)

Answer 4

You can't use custom functions inside direct queries to you database. Instead you can do something like this:
rows = questions.AsEnumerable()
//or select just that you want questions.Select(q=> new {g.Id, q.Votes,q.Title})
.Select(p=> new {
id = p.Id,
cell = new string[] { SqlFunctions.StringConvert((double)p.id), SqlFunctions.StringConvert((double)p.total_rec_days), p.year }
}).ToArray()
That should work.