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.