Select list is null. Why?

See more:

MVC

C#7.0

ASP.NET-Core

Error  
An unhandled exception occurred while processing the request.
ArgumentNullException: Value cannot be null. (Parameter 'items')
Microsoft.AspNetCore.Mvc.Rendering.MultiSelectList..ctor(IEnumerable items, string dataValueField, string dataTextField, IEnumerable selectedValues, string dataGroupField)

Stack Query Cookies Headers Routing
ArgumentNullException: Value cannot be null. (Parameter 'items')
Microsoft.AspNetCore.Mvc.Rendering.MultiSelectList..ctor(IEnumerable items, string dataValueField, string dataTextField, IEnumerable selectedValues, string dataGroupField)
Microsoft.AspNetCore.Mvc.Rendering.SelectList..ctor(IEnumerable items, string dataValueField, string dataTextField, object selectedValue)
Microsoft.AspNetCore.Mvc.Rendering.SelectList..ctor(IEnumerable items, string dataValueField, string dataTextField)
CallSite.Target(Closure , CallSite , Type , object , string , string )
System.Dynamic.UpdateDelegates.UpdateAndExecute4<t0, t1,="" t2,="" t3,="" tret="">(CallSite site, T0 arg0, T1 arg1, T2 arg2, T3 arg3)
AspNetCoreGeneratedDocument.Areas_admin_Views_Item_Edit.<executeasync>b__26_0() in Edit.cshtml
+

Error in this line:

<div class="form-group">
@ResAdmin.lblCategoryName

What I have tried:

class TbItem:

  1  using Sq.Models;
  2  
  3  namespace Sq.BL
  4  {
  5      public class ClsItems
  6      {
  7          LapShopContext contnxt = new LapShopContext();
  8       
  9          public List<tbitem> GetAll()
 10          {
 11              try
 12              {
 13                  return contnxt.TbItems.ToList();
 14              }
 15              catch (Exception)
 16              {
 17                  return new List<tbitem>();
 18              }
 19          }
 20  
 21          public List<vwitem> GetAllItemData(int? CategoryId)
 22          {
 23              try
 24              {
 25  
 26                  return contnxt.VwItems.Where(srch=> 
 27                  (srch.CategoryId==CategoryId||CategoryId==null||
 28                   CategoryId==0)).ToList();
 29              }
 30              catch (Exception)
 31              {
 32                  return new List<vwitem>();
 33              }
 34          }
 35  
 36          public TbItem GetById(int? id)
 37          {
 38              try
 39              {
 40                 // LapShopContext dbSoqContext = new LapShopContext();
 41                  var item = contnxt.TbItems.FirstOrDefault
 42                             (c => c.ItemId == id);
 43  
 44                  return item;
 45              }
 46              catch
 47              {
 48                  return new TbItem();
 49              }
 50          }
 51  
 52          public bool Save(TbItem item)
 53          {
 54              try
 55              {
 56                  LapShopContext ctx = new LapShopContext();
 57  
 58                  if (item.ItemId == 0)
 59                  {
 60                      item.CreatedBy = "xm";
 61                      item.CreatedDate = DateTime.Now;
 62                      ctx.TbItems.Add(item);
 63                  }
 64                  else
 65                  {
 66                      item.CreatedBy = "xm";
 67                      item.CreatedDate = DateTime.Now;
 68                      ctx.Entry(item).State = 
 69                      Microsoft.EntityFrameworkCore.EntityState.Modified;
 70                  }
 71  
 72                  ctx.SaveChanges();
 73                  return true;
 74              }
 75              catch (Exception)
 76              {
 77                  return false;
 78              }
 79          }
 80  
 81          public bool Delete(int id)
 82          {
 83              try
 84              {
 85                  LapShopContext ctx = new LapShopContext();
 86                  var item = GetById(id);
 87                  ctx.TbItems.Remove(item);
 88  
 89                  ctx.SaveChanges();
 90                  return true;
 91              }
 92              catch (Exception)
 93              {
 94                  return false;
 95              }
 96          }
 97      }
 98  }

My controller:

  1  using Microsoft.AspNetCore.Mvc;
  2  using Sq.BL;
  3  using Sq.Models;
  4  using Sq.Utilities;
  5  
  6  namespace Sq.Areas.admin.Controllers
  7  {
  8      [Area("admin")]
  9      public class ItemController : Controller
 10      {
 11          ClsItems clsItem = new ClsItems();
 12          ClsCategory catList = new ClsCategory();
 13          ClsOs ClsOs = new ClsOs();
 14  
 15          public IActionResult List()
 16          {
 17              ClsItemTypes ClsItemTypes = new ClsItemTypes();
 18              ViewBag.lstItemTypes = ClsItemTypes.GetAll();
 19              ViewBag.lstCategories = catList.GetAll();
 20              var lstItem=clsItem.GetAllItemData(null);   
 21              return View(lstItem);
 22          }
 23         
 24          public ActionResult Edit(int? ItemId)
 25          {
 26              ClsItemTypes ClsItemTypes = new ClsItemTypes();
 27              var item = new Models.TbItem();
 28              ViewBag.lstCategories = catList.GetAll();
 29              ViewBag.lstItemTypes = ClsItemTypes.GetAll();
 30              ViewBag.lstOs = ClsOs.GetAll();
 31  
 32              if (ItemId != null)
 33              {
 34                  item = clsItem.GetById(ItemId);
 35              }
 36  
 37              return View(item);
 38          }
 39  
 40          [HttpPost]
 41          [ValidateAntiForgeryToken]
 42          public async Task<actionresult> 
 43          Save(TbItem item, List<iformfile> Files)
 44          {
 45              if (!ModelState.IsValid)
 46  
 47                  return View("Edit", item);
 48              item.ImageName = await Helper.UploadImage(Files, "items");
 49              clsItem.Save(item);
 50              return RedirectToAction("List");
 51          }
 52  
 53          public IActionResult Search(int id)
 54          {
 55              ViewBag.lstCategories = catList.GetAll();
 56              var items = clsItem.GetAllItemData(id);
 57              return View("List",items);
 58          }
 59      }
 60  }

Error in View Or my Design in this Line:

<div class="form-group">
    @ResAdmin.lblCategoryName
    
    <span></span>
</div>

If you see my all page
this is my Design:

  1  @model TbItem
  2  
  3  <div class="content-wrapper">
  4      <div class="page-header">
  5          <h3 class="page-title"> Form elements </h3>
  6          
  7              <ol class="breadcrumb">
  8                  <li class="breadcrumb-item">
  9                  <a href="#">Forms</a></li> 
 10                  <li class="breadcrumb-item active">
 11                  Form elements</li>
 12              </ol>        
 13      </div>    
 14          <div class="row">
 15  
 16              <div class="col-md-6 grid-margin stretch-card">
 17                  <div class="card">
 18                      <div class="card-body">
 19                          <h4 class="card-title">
 20                              Default form</h4>
 21                          <p class="card-description"> 
 22                              Basic form layout </p>                        
 23                          
 24                          <div class="form-group">
 25                              @ResAdmin.lblItemName
 26                              
 27                              <span></span>
 28                          </div>
 29  
 30                          <div class="form-group">
 31                              @ResAdmin.lblCategoryName
 32                              
 33                              <span></span>
 34                          </div>
 35  
 36                          <div class="form-group">
 37                              @ResAdmin.lblItemType
 38                              
 39                              <span></span>
 40                          </div>
 41  
 42                          <div class="form-group">
 43                              @ResAdmin.lblOs
 44                              
 45                              <span></span>
 46                          </div>
 47  
 48                          <div class="form-group">
 49                              @ResAdmin.lblSalesPrice
 50                              
 51                              <span></span>
 52                          </div>
 53  
 54                          <div class="form-group">
 55                              @ResAdmin.lblPurchasePrice
 56                              
 57                              <span></span>
 58                          </div>
 59  
 60                          <div class="form-group">
 61                              @ResAdmin.lblWeight                            
 62                              
 63                          </div>
 64  
 65                          <div class="form-group">
 66                              
 67                                  @ResAdmin.lblImage                            
 68  
 69                          </div>
 70  
 71                          @ResGeneral.lblSave
 72                          @ResGeneral.lblNew
 73  
 74                      </div>
 75                  </div>
 76              </div>
 77  
 78              <div class="col-md-6 grid-margin stretch-card">
 79                  <div class="card">
 80                      <div class="card-body">
 81                          <h4 class="card-title">
 82                          Main Data</h4>
 83                          <p class="card-description"> 
 84                          Basic form layout </p>
 85  
 86                          <div class="form-group">
 87                              @ResAdmin.lblGpu                            
 88                              
 89                          </div>
 90  
 91                          <div class="form-group">
 92                              @ResAdmin.lblProcessor                            
 93                              
 94                          </div>
 95  
 96                          <div class="form-group">
 97                              @ResAdmin.lblHardDisk                            
 98                              
 99                          </div>
100  
101                          <div class="form-group">
102                              @ResAdmin.lblRamSize                            
103                              
104                          </div>
105  
106                          <div class="form-group">
107                              @ResAdmin.lblScreenReslution                            
108                              
109                          </div>
110  
111                          <div class="form-group">
112                              @ResAdmin.lblScreenSize                            
113                              
114                          </div>
115                          <span id="tbImgName"></span>
116                          <div id="tbImgSrc">
117                              
118                          </div>
119                      </div>
120                  </div>
121              </div>
122  
123          </div>
124      
125  </div>
126  @section Scripts
127  {    
128          var Upload = {
129              UploadDefaultImg: function (e) {
130                  const file = e.target.files[0];
131                  const reader = new FileReader();
132                  reader.onloadend = () => {
133                      CourseMediaImgName = file.name;
134                      CourseMediaImgBase64 = reader.result.slice
135                      (reader.result.indexOf('base64,') + 7);
136                      $("#tbImgName").html(file.name)
137                      $("#tbImgSrc").html(`<img class="thumbnail" 
138                      src = "${reader.result}"  
139                      style = "width: 200px;
140                      height: 300px;border-radius: 5px;
141                      border: 1px solid #d9d9d9;padding: 1px;" />`)
142                  };
143                  reader.readAsDataURL(file);
144              }
145          }    
146  }</div>