Database First EF6 add data to table with Custom ViewModel - entity-framework-6

Question

I using MVC 5.1 and EF 6.1 database first model. I don't like the view that was created by the scaffolding as it uses all the database columns. On the create view I just want the user to input the required fields all other data can be added through editing the details view. I have created the a view model to use other than the .edmx generated one. The view works as expected but when the create action button is click the post operation dies with a "[NullReferenceException: Object reference not set to an instance of an object.]
Here is my view model
public class DesktopCreateViewModel
{
[Required]
[Display(Name = "Serial Number")]
[StringLength(30)]
public string SERIAL_NUMBER { get; set; }
public int Model_DesktopId { get; set; }
public int DeviceType_DesktopId { get; set; }
[Required]
[StringLength(50)]
public string MAC1 { get; set; }
[Display(Name = "Arrival Date")]
public DateTime ARRIVAL_DATE { get; set; }
[Timestamp]
[Display(Name = "Record Updated")]
public DateTime RECORD_UPDATED { get; set; }
public int LocationId { get; set; }
public int Location_CodeId { get; set; }
public int MemoryId { get; set; }
public int MonitorId { get; set; }
public int PlantId { get; set; }
public int DepartmentId { get; set; }
public int Operating_SystemId { get; set; }
[ForeignKey("DeparmentId")]
public virtual Department Department { get; set; }
[ForeignKey("DeviceType_DesktopId")]
public virtual DeviceType_Desktop DeviceType_Desktop { get; set; }
[ForeignKey("Location_CodeId")]
public virtual Location_Code Location_Code { get; set; }
[ForeignKey("LocationId")]
public virtual Location Location { get; set; }
[ForeignKey("MemoryId")]
public virtual Memory Memory { get; set; }
[ForeignKey("Model_DesktopId")]
public virtual Model_Desktop Model_Desktop { get; set; }
[ForeignKey("MonitorId")]
public virtual Monitor Monitor { get; set; }
[ForeignKey("Operating_SystemId")]
public virtual Operating_System Operating_System { get; set; }
[ForeignKey("PlantId")]
public virtual Plant Plant { get; set; }
public IEnumerable<DesktopCreateViewModel> Create_Desktop { get; set; }
public virtual ICollection<DesktopCreateViewModel> Desktops { get; set; }
Here is the portion of the controller that fails
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create(ICollection<DesktopCreateViewModel> desktop)
{
if (ModelState.IsValid)
{
foreach (var item in desktop)
{
db.Entry(desktop).State = EntityState.Added;
}
db.SaveChanges();
return RedirectToAction("Index");
}
ViewBag.DepartmentId = new SelectList(db.Departments, "Id", "DEPARTMENT1", desktop.DepartmentId);
ViewBag.DeviceType_DesktopId = new SelectList(db.DeviceType_Desktop, "Id", "DEVICE_TYPE", desktop.DeviceType_DesktopId);
ViewBag.Location_CodeId = new SelectList(db.Location_Code, "Id", "LOCATION_CODE1", desktop.Location_CodeId);
ViewBag.LocationId = new SelectList(db.Locations, "Id", "LOCATION1", desktop.LocationId);
ViewBag.MemoryId = new SelectList(db.Memories, "Id", "MEMORY1", desktop.MemoryId);
ViewBag.Model_DesktopId = new SelectList(db.Model_Desktop, "Id", "MODEL", desktop.Model_DesktopId);
ViewBag.MonitorId = new SelectList(db.Monitors, "Id", "MONITOR1", desktop.MonitorId);
ViewBag.Operating_SystemId = new SelectList(db.Operating_System, "Id", "OS", desktop.Operating_SystemId);
ViewBag.PlantId = new SelectList(db.Plants, "Id", "PLANT1", desktop.PlantId);
return View(desktop);
}
This is the View
#using (Html.BeginForm())
{
#Html.AntiForgeryToken()
<div class="form-horizontal">
<h4>Desktop</h4>
<hr />
#Html.ValidationSummary(true)
<div class="form-group">
#Html.LabelFor(model => model.SERIAL_NUMBER, new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.EditorFor(model => model.SERIAL_NUMBER)
#Html.ValidationMessageFor(model => model.SERIAL_NUMBER)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.Model_DesktopId, "Model", new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.DropDownList("Model_DesktopId", String.Empty)
#Html.ValidationMessageFor(model => model.Model_DesktopId)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.DeviceType_DesktopId, "Device Type", new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.DropDownList("DeviceType_DesktopId", String.Empty)
#Html.ValidationMessageFor(model => model.DeviceType_DesktopId)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.MAC1, new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.EditorFor(model => model.MAC1)
#Html.ValidationMessageFor(model => model.MAC1)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.ARRIVAL_DATE, new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.EditorFor(model => model.ARRIVAL_DATE)
#Html.ValidationMessageFor(model => model.ARRIVAL_DATE)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.RECORD_UPDATED, new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.EditorFor(model => model.RECORD_UPDATED)
#Html.ValidationMessageFor(model => model.RECORD_UPDATED)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.LocationId, "Location", new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.DropDownList("LocationId", String.Empty)
#Html.ValidationMessageFor(model => model.LocationId)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.Location_CodeId, "Location Code", new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.DropDownList("Location_CodeId", String.Empty)
#Html.ValidationMessageFor(model => model.Location_CodeId)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.MemoryId, "Memory", new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.DropDownList("MemoryId", String.Empty)
#Html.ValidationMessageFor(model => model.MemoryId)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.MonitorId, "Monitor", new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.DropDownList("MonitorId", String.Empty)
#Html.ValidationMessageFor(model => model.MonitorId)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.PlantId, "Plant", new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.DropDownList("PlantId", String.Empty)
#Html.ValidationMessageFor(model => model.PlantId)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.DepartmentId, "Department", new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.DropDownList("DepartmentId", String.Empty)
#Html.ValidationMessageFor(model => model.DepartmentId)
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.Operating_SystemId, "Operating System", new { #class = "control-label col-md-4" })
<div class="col-md-8">
#Html.DropDownList("Operating_SystemId", String.Empty)
#Html.ValidationMessageFor(model => model.Operating_SystemId)
</div>
</div>
<div class="form-group">
<div class="col-md-offset-8 col-md-4">
<input type="submit" value="Create" class="btn btn-default" />
</div>
</div>
</div>
}
<div>
#Html.ActionLink("Back to List", "Index")
</div>
#section Scripts {
#Scripts.Render("~/bundles/jqueryval")
}

Answer 1

The action is expecting a collection of viewmodels (ICollection<DesktopCreateViewModel>), but the view only contains one. Try changing to:
public ActionResult Create(DesktopCreateViewModel desktop)