C# 字符串序列号{get；set；} 公共字符串资产\标记\编号{get；set；} 公共约会时间？获取日期{get；set；} 公共约会时间？disposed_date{get；set；} 公共约会时间？已验证的_日期{get；set；} 创建的公共日期时间\u日期{get；set；} 由{get；set；}创建的公共字符串 公共约会时间？修改的_日期{get；set；} 由{get；set；}修改的公共字符串 } 公共枚举任务 { 型号=1， 制造商=2， 类型=3， 位置=4， 供应商=5， 状态=6， ip_地址=7， mac_地址=8， 注=9， 所有者=10， 成本=11， 采购订单编号=12， 描述=13， 发票号=14， 序列号=15， 资产标签编号=16， 获得日期=17， 处理日期=18， 验证日期=19， 创建日期=20， 创建单位=21， 修改日期=22， 修改的_=23 } 公共IQueryable DynamicSelectionColumns（） { 使用（var db=new TrackerDataContext（）） { 字符串fieldId=“，”+“4,5,3,2,6,17,11,12”+”； var taskColum=Enum.GetValues（typeof（EnumTasks））.Cast（）。其中（e=>fieldIds.Contains（“，”+（（int）e）.ToString（）+“，”）。选择（e=>e.ToString（）.Replace（“，”）； string select=“new（TaskId，”+（taskColumn.Count（）>0？string.Join（“，”，taskColumn）+”，“：”）+“Id”）； 返回db.Task.ToList（），CreatedDate=t.CreatedDate，Details=t.Details，EstimatedTime=t.EstimatedTime，FileName=t.FileName，LogWork=t.LogWork，Module=t.Module！=null？t.Module.Name:，Priority=t.Priority！=null？t.Priority.Name:，Project=t.Project！=null？t.Project.Name:“，ResolveDate=t.ResolveDate，Status=t.Status！=null？t.Status.Name:，Subject=t.Subject，TaskType=t.TaskType！=null？t.TaskType.Type:，Version=t.Version！=null？t.Version.Name:：}）.ToList（）.AsQueryable（）.Select（Select）； } } }

在何处/如何设置此代码以使用

Linq DynamicColumns（）

？

代码优先是实体框架的一种方法。查询数据库也是实体框架。那么你的问题是关于MVC还是EF？如果是EF，那么为什么要发布标记。发布您的数据访问层代码@abatishchev，发布我的数据访问层代码？如果您已经编写了如何处理用户输入以选择字段，那么现在就足够了。请发布如何查询数据库（使用EF？）。是的，通常我在控制器中使用EF/LINQ进行查询。（例如）：

INV\u Assets asset=db.INV\u Assets.Find（资产ID）public class ExportAssetsViewModel
{
    public Dictionary<int, string> ListOfExportFields { get; set; }
    public int[] SelectedFields { get; set; }

    public ExportAssetsViewModel() {
        ListOfExportFields = new Dictionary<int, string>() {
            {1, "Model"},
            {2, "Manufacturer"},
            {3, "Type"},
            {4, "Location"},
            {5, "Vendor"},
            {6, "Status"},
            {7, "ip_address"},
            {8, "mac_address"},
            {9, "note"},
            {10, "owner"},
            {11, "cost"},
            {12, "po_number"},
            {13, "description"},
            {14, "invoice_number"},
            {15, "serial_number"},
            {16, "asset_tag_number"},
            {17, "acquired_date"},
            {18, "disposed_date"},
            {19, "verified_date"},
            {20, "created_date"},
            {21, "created_by"},
            {22, "modified_date"},
            {23, "modified_by"},
        };
    }
}

    public ActionResult Index()
    {
        ExportAssetsViewModel expViewMod = new ExportAssetsViewModel();
        return View(expViewMod);
    }

@model InventoryTracker.Models.ExportAssetsViewModel

@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Export</h2>

<p>Please select which Asset fields to Export to Excel:</p>

@using (Html.BeginForm("ExportUsingEPPlus", "Export", FormMethod.Post))
{
    @Html.ListBoxFor(m => m.SelectedFields, new MultiSelectList(Model.ListOfExportFields, "Key", "Value"), new { @class = "form-control", style = "height: 250px;" })
    <br />
    <input type="submit" value="ExportUsingEPPlus" />
}

<h2>Export</h2>

<p>Please select which Asset fields to Export to Excel:</p>

<form action="/Export/ExportUsingEPPlus" method="post"><select class="form-control" id="SelectedFields" multiple="multiple" name="SelectedFields" style="height: 250px;"><option value="1">Model</option>
<option value="2">Manufacturer</option>
<option value="3">Type</option>
<option value="4">Location</option>
<option value="5">Vendor</option>
<option value="6">Status</option>
<option value="7">ip_address</option>
<option value="8">mac_address</option>
<option value="9">note</option>
<option value="10">owner</option>
<option value="11">cost</option>
<option value="12">po_number</option>
<option value="13">description</option>
<option value="14">invoice_number</option>
<option value="15">serial_number</option>
<option value="16">asset_tag_number</option>
<option value="17">acquired_date</option>
<option value="18">disposed_date</option>
<option value="19">verified_date</option>
<option value="20">created_date</option>
<option value="21">created_by</option>
<option value="22">modified_date</option>
<option value="23">modified_by</option>
</select>    <br />
    <input type="submit" value="ExportUsingEPPlus" />
</form>

    [HttpPost]
    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);
        }

        // 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();
        }

        // INVALID - Need to query table INV_Assets for all values of selected fields and insert into appropriate columns.
        if (exportFields.Count() > 0)
        {
            ws.Cells["A2"].LoadFromCollection(exportFields);
        }

        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);

[ip_address]
[mac_address]
[note]
[owner]
[cost]

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using GridMvc.DataAnnotations;
using System.Web.Mvc;
using InventoryTracker.Models;

namespace InventoryTracker.Models
{
    [GridTable(PagingEnabled = true, PageSize = 30)]
    public class INV_Assets 
    {
        // Setting GridColumn Annotations allows you to use AutoGenerateColumns on view to auto create the Grid based on the model.


        public int Id { get; set; }

        public int Model_Id { get; set; }
        [ForeignKey("Model_Id")]
        public virtual INV_Models Model { get; set; }

        [Required]
        public int Manufacturer_Id { get; set; }
        [ForeignKey("Manufacturer_Id")]
        public virtual INV_Manufacturers Manufacturer { get; set; }

        [Required]
        public int Type_Id { get; set; }
        [ForeignKey("Type_Id")]
        public virtual INV_Types Type { get; set; }

        [Required]
        public int Location_Id { get; set; }
        [ForeignKey("Location_Id")]
        public virtual INV_Locations Location { get; set; }

        public int Vendor_Id { get; set; }
        [ForeignKey("Vendor_Id")]
        public virtual INV_Vendors Vendor { get; set; }

        [Required]
        public int Status_Id { get; set; }
        [ForeignKey("Status_Id")]
        public virtual INV_Statuses Status { get; set; }

        public string ip_address { get; set; }

        public string mac_address { get; set; }

        [DataType(DataType.MultilineText)]
        public string note { get; set; }
        public string owner { get; set; }

        //[DataType(DataType.Currency)]
        //[DisplayFormat(DataFormatString="{0:C}", ApplyFormatInEditMode=true)]
        [DisplayFormat(DataFormatString = "{0:#,###0.00}", ApplyFormatInEditMode=true)]
        public decimal cost { get; set; }
        public string po_number { get; set; }

        [DataType(DataType.MultilineText)]
        public string description { get; set; }

        public int invoice_number{ get; set; }

        [Required]
        public string serial_number { get; set; }

        [Required]
        public string asset_tag_number { get; set; }

        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
        public DateTime? acquired_date { get; set; }

        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
        public DateTime? disposed_date { get; set; }

        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
        public DateTime? verified_date { get; set; }

        [Required]
        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
        public DateTime created_date { get; set; }

        [Required]
        public string created_by { get; set; }

        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}")]
        public DateTime? modified_date { get; set; }

        public string modified_by { get; set; }

        // Flag to specify if item is available? (Not signed out, not auctioned, recycled, etc.)
        //public bool available { get; set; }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;
using InventoryTracker.DAL;
using OfficeOpenXml;
using InventoryTracker.Models;
using System.Linq.Dynamic;


namespace InventoryTracker.Controllers
{
    public class ExportController : Controller
    {
        InventoryTrackerContext _db = new InventoryTrackerContext();

        // GET: Export
        public ActionResult Index()
        {
            ExportAssetsViewModel expViewMod = new ExportAssetsViewModel();
            return View(expViewMod);
        }

        public ActionResult Export()
        {
            GridView gv = new GridView();
            gv.DataSource = _db.INV_Assets.ToList();
            gv.DataBind();
            Response.ClearContent();
            Response.Buffer = true;
            Response.AddHeader("content-disposition", "attachment; filename=InventoryAssets-" + DateTime.Now + ".xls");
            Response.ContentType = "application/ms-excel";
            Response.Charset = "";
            StringWriter sw = new StringWriter();
            HtmlTextWriter htw = new HtmlTextWriter(sw);
            gv.RenderControl(htw);
            Response.Output.Write(sw.ToString());
            Response.Flush();
            Response.End();

            return RedirectToAction("StudentDetails");
        }

        [HttpPost]
        public ActionResult ExportUsingEPPlus(ExportAssetsViewModel model)
        {
            //FileInfo newExcelFile = new FileInfo(output);
            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);
            }

            // 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();
            }

            // INVALID - Need to query table INV_Assets for all values of selected fields and insert into appropriate columns.
            if (exportFields.Count() > 0)
            {
                var exportAssets = from ia in _db.INV_Assets
                                   select new {
                                       ia.ip_address,

                                   }
                ws.Cells["A2"].LoadFromCollection(exportFields);
            }

            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 class DynamicColumns : INV_Assets
    {
        //public int Id { get; set; }
        //public int Model_Id { get; set; }
        public virtual INV_Models Model { get; set; }
        //public int Manufacturer_Id { get; set; }
        public virtual INV_Manufacturers Manufacturer { get; set; }
        //public int Type_Id { get; set; }
        public virtual INV_Types Type { get; set; }
        //public int Location_Id { get; set; }
        public virtual INV_Locations Location { get; set; }
        //public int Vendor_Id { get; set; }
        public virtual INV_Vendors Vendor { get; set; }
        //public int Status_Id { get; set; }
        public virtual INV_Statuses 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
    }

     public IQueryable DynamicSelectionColumns()
    {
        using (var db = new TrackerDataContext())
        {
            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 )";

            return db.Task.ToList().Select(t => new DynamicColumns() { Id = t.Id, TaskId = Project != null ? Project.Alias + "-" + t.Id : t.Id.ToString(), ActualTime = t.ActualTime, AssignedBy = t.AssignedBy.ToString(), AssignedDate = t.AssignedDate, AssignedTo = t.AssignedTo.ToString(), CreatedDate = t.CreatedDate, Details = t.Details, EstimatedTime = t.EstimatedTime, FileName = t.FileName, LogWork = t.LogWork, Module = t.Module != null ? t.Module.Name : "", Priority = t.Priority != null ? t.Priority.Name : "", Project = t.Project != null ? t.Project.Name : "", ResolveDate = t.ResolveDate, Status = t.Status != null ? t.Status.Name : "", Subject = t.Subject, TaskType = t.TaskType != null ? t.TaskType.Type : "", Version = t.Version != null ? t.Version.Name : "" }).ToList().AsQueryable().Select(select);
        }
    }
}