访问IQueryable / System.Collections.Generic.List的内容？

Question

I have an MVC5/Code-First application I'm developing using Entity Framework. Currently I'm trying to add Export to Excel functionality to output user selected properties of my INV_Assets model dynamically. Using the EPPlus Libary and Linq.Dynamic I have managed to export my data to excel, but not quite correctly.

I've gotten the Headers to export into Row 1, but I'm still having difficulty getting the data to export. Currently the data for my selected fields all comes across, but each value is exported as a long string into it's own row in Column A. For example, if I select the following fields (Status, ip_address, mac_address, note, owner, cost, po_number, and description) I get the following:

Row1: [Status][ip_address][mac_address][note][owner][cost][po_number][description]

Row2: [{Status=SIGNEDOUT, ip_address=10.10.121.25, mac_address=10.10.134.11, note=, owner=John Smith, cost=35.00, po_number=G348, description=This is a description of the item.}][][][][][][][]

Here is a visual of the output I'm currently getting in Excel:

When I set my IQueryable variable ( selectStatement ) as a Watch variable in VS2013 I am able to drill down into the contents, but I can't figure out how to access these contents individually in code:

Currently I use my IQueryable and load it into Excel via the EPPlus LoadFromCollection() method, but if I can figure out how to access individual contents of my IQueryable I can then set up some counters and loops to appropriately set the cells I want instead of everything dumping into ColumnA.

Can anyone assist with this? Full code for my ExportController below:

    public ActionResult ExportUsingEPPlus(ExportAssetsViewModel model)
    {
        ExcelPackage package = new ExcelPackage();
        var ws = package.Workbook.Worksheets.Add("TestExport");

        var exportFields = new List<string>();
        foreach (var selectedField in model.SelectedFields)
        {
            // Adds selected fields to [exportFields] List<string>
            exportFields.Add(model.ListOfExportFields.First(s => s.Key == selectedField).Value);
        }

        IQueryable selectStatement = DynamicSelectionColumns(exportFields);

        // Loops to insert column headings into Row 1 of Excel
        for (int i = 0; i < exportFields.Count(); i++)
        {
            ws.Cells[1, i + 1].Value = exportFields[i].ToString();
        }

        // Place contents of IQueryable into Excel -- currently dumps selected value for each record into rows with all values for the row as a long string in ColumnA
        if (selectStatement.Count() > 0)
        {
            ws.Cells["A2"].LoadFromCollection(selectStatement.Cast<object>(), true);
        }

        int cnt = 20;
        foreach (var item in selectStatement)
        {
            ws.Cells["A" + cnt].LoadFromCollection(selectStatement.Cast<object>(), false);
            cnt++;

        }


        var memoryStream = new MemoryStream();
        package.SaveAs(memoryStream);

        string fileName = "Exported-InventoryAssets-" + DateTime.Now + ".xlsx";
        string contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";

        memoryStream.Position = 0;
        return File(memoryStream, contentType, fileName);
    }

    public IQueryable DynamicSelectionColumns(List<string> fieldsForExport)
    {
        using (var db = new InventoryTrackerContext())
        {
            string fieldIds = "," + "4,5,3,2,6,17,11,12" + ",";

            var taskColum = Enum.GetValues(typeof(EnumTasks)).Cast<EnumTasks>().Where(e => fieldIds.Contains("," + ((int)e).ToString() + ",")).Select(e => e.ToString().Replace("_", ""));

            //string select = "new (  TaskId, " + (taskColum.Count() > 0 ? string.Join(", ", taskColum) + ", " : "") + "Id )";
            string select = "new (  " + string.Join(", ", fieldsForExport) + ")";

            //return db.INV_Assets.ToList().Select(t => new DynamicColumns() { Id = t.Id, TaskId = Project != null ? Project.Alias + "-" + t.Id : t.Id.ToString(), 
            return db.INV_Assets.ToList().Select(t => new DynamicColumns()
            {
                Id = t.Id,
                Manufacturer = Convert.ToString(t.Manufacturer.manufacturer_description),
                Type = t.Type.type_description,
                Location = t.Location.location_room,
                Vendor = t.Vendor.vendor_name,
                Status = t.Status.status_description,
                ip_address = t.ip_address,
                mac_address = t.mac_address,
                note = t.note,
                owner = t.owner,
                //Module = t.Module != null ? t.Module.Name : "", 
                cost = t.cost,
                po_number = t.po_number,
                description = t.description,
                invoice_number = t.invoice_number,
                serial_number = t.serial_number,
                asset_tag_number = t.asset_tag_number,
                acquired_date = t.acquired_date,
                disposed_date = t.disposed_date,
                verified_date = t.verified_date,
                created_date = t.created_date,
                created_by = t.created_by,
                modified_date = t.modified_date,
                modified_by = t.modified_by
            }).ToList().AsQueryable().Select(select);
        }
    }
}

public class DynamicColumns : INV_Assets
{
    public string Model { get; set; }
    public string Manufacturer { get; set; }
    public string Type { get; set; }
    public string Location { get; set; }
    public string Vendor { get; set; }
    public string Status { get; set; }
    public string ip_address { get; set; }
    public string mac_address { get; set; }
    public string note { get; set; }
    public string owner { get; set; }
    public decimal cost { get; set; }
    public string po_number { get; set; }
    public string description { get; set; }
    public int invoice_number { get; set; }
    public string serial_number { get; set; }
    public string asset_tag_number { get; set; }
    public DateTime? acquired_date { get; set; }
    public DateTime? disposed_date { get; set; }
    public DateTime? verified_date { get; set; }
    public DateTime created_date { get; set; }
    public string created_by { get; set; }
    public DateTime? modified_date { get; set; }
    public string modified_by { get; set; }
}

public enum EnumTasks
{
    Model = 1,
    Manufacturer = 2,
    Type = 3,
    Location = 4,
    Vendor = 5,
    Status = 6,
    ip_address = 7,
    mac_address = 8,
    note = 9,
    owner = 10,
    cost = 11,
    po_number = 12,
    description = 13,
    invoice_number = 14,
    serial_number = 15,
    asset_tag_number = 16,
    acquired_date = 17,
    disposed_date = 18,
    verified_date = 19,
    created_date = 20,
    created_by = 21,
    modified_date = 22,
    modified_by = 23
}

Answer 1

The output you are getting in your non-header cells:

Status=SIGNEDOUT, ip_address=10.10.121.25, mac_address=10.10.134.11, note=, owner=John Smith, cost=35.00, po_number=G348, description=This is a description of the item.

looks like the object represented as property=value , separated by commas. I would guess that the object's ToString() method is overridden and creating that output.

Since you are casting your strongly typed objects to System.Object

selectStatement.Cast<object>()

that is probably the best that EPPlus can do.

Try not casting it to System.Object, eg

ws.Cells["A2"].LoadFromCollection(selectStatement, true);

Here's an article that shows proper use of LoadFromCollection

http://www.sitecorecleveland.com/resources/blogs-posts/easy_excel_interaction_pt5

UPDATE

The error

The type arguments for method 'OfficeOpenXml.ExcelRangeBase.LoadFromCollection(System.Collection.Generic.IE‌​numerable, bool)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

is telling you that you need to specify the actual type returned by the query (rather than specifying object ).

ws.Cells["A2"].LoadFromCollection(selectStatement.Cast<DynamicColumns>(), true);