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How to pass collection from view to controller in asp.net MVC4

I want to pass a collection of skills id from my view to controller action, i have a dropdownlist of SKILLS :
<select name="skills">
<option value="0">Java</option>
<option value="1">C++</option>
<option value="2">Fortran</option>
<option value="3">ASP</option>
</select>
i want that user can select many skills from dropdown and store their value in a collection ,i.e an array, and then post that array to action in controller as follow [employee and skills have a manytomany relationship]:
[HttpPost]
public ActionResult AddEmp(Employee emp ,IEnumerable<Skills> skills )
{
DBCtx db=new DbCtx();
db.employees.Add(emp);
var emp_id=db.SaveChanges();
var employee=db.employees.Find(emp_id);
foreach(item in skills)
{
var skill = db.skills.Find(item);
employee.skills.Add(skill);
}
db.SaveChanges();
return View();
}
How can i achieve this ,thanks in advance ....

You have quite few options on front end . Razor, Angular, Jquery... To simplfy things in following example i have used Razor view. I dont think you need to pass Skills as a strongly type object as you only need Id of selected Skills . Also in the example i have the skills list static / hard coded into razor view, ideally it should be bound from backend.
Saying that lets assume our Employee View Model as it follows
public class EmployeeViewModel
{
public EmployeeViewModel()
{
SelectedSkills=new List<int>();
}
public int Id { get; set; }
public string Name { get; set; }
public List<int> SelectedSkills { get; set; }
}
public class Skills
{
public int Id { get; set; }
public string Name { get; set; }
}
Then our Controller (EmployeeController.cs) would be .(please ignore the EF logic after data is bound to class)
public class EmployeeController : Controller
{
public ActionResult Index()
{
return View("Employee",new EmployeeViewModel());
}
[HttpPost]
public ActionResult AddEmp(EmployeeViewModel employee)
{
var idOfEmployee=AddEmployee(employee);
foreach (var item in employee.SelectedSkills)
{
AddSkill(idOfEmployee,item);
}
return View("Employee");
}
private void AddSkill(int idOfEmployee, int skillId)
{
// your EF logic
}
private int AddEmployee(EmployeeViewModel emp)
{
// your EF logic, get your id of the inserted employee
return 0;
}
}
Then our Employee.cshtml view could be
#using System.Web.UI.WebControls
#using WebApplication4.Controllers
#model WebApplication4.Controllers.EmployeeViewModel
#{
ViewBag.Title = "Employee";
}
<h2>Employee</h2>
#{var listItems = new List<Skills>
{
new Skills { Id = 0,Name="Java" },
new Skills { Id = 1,Name="C++" },
new Skills { Id = 2,Name="Fortran" }
};
}
#using (Html.BeginForm("AddEmp", "Employee"))
{
#Html.TextBoxFor(m => m.Name, new { autofocus = "New Employee" })
<br/>
#Html.ListBoxFor(m => m.SelectedSkills,
new MultiSelectList(listItems, "Id", "Name",#Model.SelectedSkills)
, new { Multiple = "multiple" })
<input type="submit" value="Submit" class="submit"/>
}

Dropdownlist from database in MVC5

ViewModel:
public class GroepModel
{
public int id { get; set; }
public String Naam { get; set; }
public String Beschrijving { get; set; }
}
Controller:
public class GroepController : Controller
{
AlinaDatabaseDataContext db = new AlinaDatabaseDataContext();
// GET: Groep
public ActionResult Groepen()
{
List<GroepModel> groepen = Mapper.Map<List<GroepenWerkvorm>, List<GroepModel>>(db.GroepenWerkvorms.ToList());
return View(groepen);
}
}
View
#model alina1617.Models.GroepModel
#{
ViewBag.Title = "Groepen";
}
<h2>Groepen</h2>
<div>
#Html.DropDownListFor(model => model. //This is not working )
</div>
I've looked around and a lot of the things I'm finding solve this using ViewBags, but isn't it suboptimal to use them? So what would be the best approach to get a dropdownlist using a model class with data from a database?

first you need to add an SelectList to your viewModel :
public class MyViewModel {
public SelectList list {get;set;}
public int selectedItem {get;set;}
}
then you need to add your list to the SelectList :
public class GroepController : Controller
{
AlinaDatabaseDataContext db = new AlinaDatabaseDataContext();
// GET: Groep
public ActionResult Groepen()
{
List<GroepModel> groepen = Mapper.Map<List<GroepenWerkvorm>, List<GroepModel>>(db.GroepenWerkvorms.ToList());
var model = new MyViewModel();
model.list = new SelectList(groepen, "id", "Naam");
return View(model);
}
}
and in the view :
#model alina1617.Models.MyViewModel
#{
ViewBag.Title = "Groepen";
}
<h2>Groepen</h2>
<div>
#Html.DropDownListFor(model => model.selectedItem, Model.list )
</div>

Submit model with SelectList in ASP.NET MVC

What I have is a form with multiple inputs that I want to use to query database for some results. Form has some default values and it all works, however I have problem submitting it to itself.
The returned error is "No paramaterless constructor defined for this object" and it is caused by SelectList object.
I have tried this solution and made psUserType private with getter and setter and intialized it as empty list, but then my dropDown menu had no values on start. Not sure why GetUserTypes hadn't filled them.
What am I doing wrong here? How does one have both preselected values and also send the same model with user-selected values, while also displaying results on the same page?
Does it make sense to use the same model for all 3 actions: 1. display form and inputs with default values 2. post selected values during submit 3. return results and selected values? I've read this solution also but not sure how to use 2 or 3 separate models here.
Any help is appreciated. Thanks in advance.
Model
public class SearchDownloadsModel
{
public SelectList psUserType { get; private set; } //causes problem on submit
public string psText { get; set; }
public MultiSelectList psColumns { get; private set; }
public IEnumerable<ResultsRowModel> psResults { get; set; }
public SearchDownloadsModel()
{
this.psUserType = GetUserTypes();
this.psColumns = GetColumns();
this.psResults = new List<ResultsRowModel>(); //empty by default
}
public SelectList GetUserTypes()
{
List<SelectListItem> items = new List<SelectListItem>()
{
new SelectListItem { Value="user", Text="Single User" },
new SelectListItem { Value="group", Text="User group" },
...
};
return new SelectList(items, "Value", "Text");
}
public MultiSelectList GetColumns()
{
List<SelectListItem> items = new List<SelectListItem>()
{
new SelectListItem { Value = "user", Text="Username" },
new SelectListItem { Value = "file", Text="Filename" },
new SelectListItem { Value = "titl", Text="Title" },
new SelectListItem { Value = "auth", Text="Author" },
...
};
return new MultiSelectList(items, "Value", "Text");
}
}
public class ResultsRowModel
{
public int ID { get; set; }
public string EventTime { get; set; }
public string FileName { get; set; }
public string FilePath { get; set; }
public string UserName { get; set; }
...
}
View
#model Proj.Models.SearchDownloadsModel
#using (Html.BeginForm("Downloads", "Home", FormMethod.Post))
{
#Html.DropDownListFor(x => x.psUserType, Model.psUserType)
#Html.TextBoxFor(x => x.psText)
#Html.ListBoxFor(x => x.psColumnsSelected, Model.psColumns, new { multiple = "multiple" })
<button type="submit" class="btn btn-primary">Search</button>
}
#if (Model.psResults != null && Model.psResults.Any())
{
<table>
<tr>
<th>User</th>
<th>File</th>
</tr>
#foreach (var row in Model.psResults)
{
<tr>
<td>#row.UserName</td>
<td>#row.FileName</td>
</tr>
}
</table>
}
Controller
[HttpGet]
public ActionResult Downloads()
{
SearchDownloadsModel model = new SearchDownloadsModel();
model.psColumnsSelected = new List<string>() { "user", "file" }; //preselected values
return View(model);
}
[HttpPost]
public ActionResult Downloads(SearchDownloadsModel model)
{
model.psResults = queryDatabase(model);
return View(model);
}
private List<ResultsRowModel> queryDatabase(SearchDownloadsModel model)
{
//...
}
EDIT: Added ResultsRowModel under SearchDownloadsModel

In ASP.NET MVC you should only put variables containing the posted or selected values in the ViewModel class. Select List items are considered extra info and are typically passed from the Action Method into the View (.cshtml) using ViewBag items.
Many of the rendering extension methods are even written specifically for such an approach, leading to code such as this:
Controller
ViewBag.PersonID = persons.ToSelectList(); // generate SelectList here
View
#Html.DropDownListFor(model => model.PersonID)
#* The above will look for ViewBag.PersonID, based on the name of the model item *#

The DropDownListFor generates a <select> element with the name of the property you bind it to. When you submit the form, that name will be included as one of the form fields and its value will be the option's value you select.
You're binding the DropDownList to a property of type SelectList (psUserType) and when your action is called, a new instance of SelectList must be created in order to bind the form field to it. First of all, the SelectList class does not have a parameterless constructor and, thus, your error. Secondly, even if a SelectList could be created as part of model binding, the <select> element is submitting a string value which wouldn't be convertible to SelectList anyways.
What you need to do is to add a string property to your SearchDownloadsModel, for example:
public string SelectedUserType { get; set; }
Then bind the dropdownlist to this property:
#Html.DropDownListFor(x => x.SelectedUserType, Model.psUserType)
When you submit the form, this new property will have the value you selected in the drop down.

Peter's answer and Stephen's comments helped me solve the problem.
Pehaps someone will find it useful.
Any further suggestions always welcome.
Model
public class PobraniaSzukajModel
{
public IEnumerable<SelectListItem> UserTypes { get; set; }
public string psSelectedUserType { get; set; }
public IEnumerable<SelectListItem> Columns { get; set; }
public IEnumerable<string> psSelectedColumns { get; set; }
public string psText { get; set; }
public ResultsModel psResults { get; set; }
}
View
#Html.ListBoxFor(x => x.psSelectedUserType, Model.Columns)
#Html.TextBoxFor(x => x.psText)
#Html.ListBoxFor(x => x.psSelectedColumns, Model.Columns)
Controller
[HttpGet]
public ActionResult Downloads()
{
SearchDownloadsModelmodel = new SearchDownloadsModel();
model.UserTypes = GetUserTypes();
model.Columns = GetColumns();
model.psColumnsSelected = new List<string>() { "user", "file" }; //preselected values
return View(model);
}
[HttpPost]
public ActionResult Downloads(SearchDownloadsModel model)
{
model.UserTypes = GetUserTypes();
model.Columns = GetColumns();
model.psResults = GetResults(model);
return View(model);
}
public SelectList GetUserTypes()
{
//...
}
public MultiSelectList GetColumns()
{
//...
}
public ResultsModel GetResults()
{
//...
}

How Post the list of items from PartialView to controller?

This is quite simple situation actually, but I can't get how to make this work. So, there is list of checkboxes rendered in PartialView. Data passed from parent ViewModel to child ViewModel in PartialView. All these wrapped by form, unfortunately I can't get the data from PartialView.
Parent ViewModel:
public class UserProgramsViewModel
{
public int Id { get; set; }
[Required(ErrorMessage = "Введите название")]
[DisplayName("Название")]
public string ProgramName { get; set; }
[DisplayName("Пользователь")]
public string UserName { get; set; }
[DisplayName("Пользователь")]
public int UserId { get; set; }
[DisplayName("Дни Программы")]
public ICollection<ProgramDaysDTO> ProgramDays { get; set; }
public IEnumerable<DaysViewModel> Days { get; set;} //Passed to Partial
}
Child ViewModel:
public class DaysViewModel
{
public int Id { get; set; }
public string DayName { get; set; }
}
Parent View:
#Html.Partial("Days", Model.Days)
PartialView (here we are using attribute name 'Days' to bind it to Parent model)
#model IEnumerable<BBN.Admin.ViewModels.DaysViewModel>
<ul class="list-group col-lg-2">
#foreach (var item in Model)
{
<li class="list-group-item"><input type="checkbox" name="Days" value="#item.Id" /> #item.DayName</li>
}
</ul>
Controller:
[HttpPost]
[RBAC]
public async Task<ActionResult> Create(UserProgramsViewModel model)
{
var groups = await _us.GetAll();
ViewBag.Users = groups.Select(x => new SelectListItem
{
Text = x.Login,
Value = x.Id.ToString()
});
var dto = new UserProgramsDTO
{
ProgramName = model.ProgramName,
UserId = model.UserId,
Days = model.Days
};
var result = await _ps.Create(dto);
if (result.IsSuccess == (BLL.Utilities.Enums.IsSuccess)Enums.IsSuccess.Success) return RedirectToAction("Index");
else return View("Create");
}

You can use FormCollection. Assign item.DayName to input's name attribute:
PartialView(fragment):
<li class="list-group-item">
<input type="checkbox" name="#(item.DayName)Days" #if (item.Id > 0) { <text>checked</text> } /> #item.DayName
</li>
Then process FormCollection parameter and fill model's Days property with it's help:
Controller:
[HttpPost]
[RBAC]
public async Task<ActionResult> Create(UserProgramsViewModel model, FormCollection formCollection)
{
model.Days = new List<DaysViewModel>();
foreach(var key in formCollection.AllKeys.Where(x => x.Contains("Days")))
model.Days.Add(new DaysViewModel { Id = formCollection[key] == "on" ? 1 : 0, DayName = key.Replace("Days", "")} );
//other stuff...
}

Have you set values for "Days" in your parent view from controller?
like Suppose your parent view name is "Parent" then you should write like this,
public ActionResult Parent()
{
UserProgramsViewModel loUser = new UserProgramsViewModel();
//Assign Your values here
View(loUser);
}
So may be you will not get Null value here.

Form submission in partial views in MVC

I am developing a simple mvc application . The code is as follows:
Model .cs:
public class CustomModel
{
public IEnumerable<lang> lstlang { get; set; }
public IEnumerable<org> lstOrg { get; set; }
}
public class lang
{
public int langid { get; set; }
public string langName { get; set; }
}
public class org
{
public int orgId { get ;set;}
public string orgName { get; set; }
}
Controller.cs
public Action Index()
{
// Get data from database and fill the model
var model = new CustomModel();
return View(model);
}
public Action Partial()
{
// Get data from database and fill the model
var model = new CustomModel();
return PartialView(model);
}
[HttpPost]
public Action Partial(FormCollection frm, CustomModel model)
{
// Get data from database and fill the model
var model = new CustomModel();
return PartialView(model);
}
Index.cshtml
#model CustomModel
#Html.TextboxFor(x => x.lang.FirstOrDefault().id);
<input type="button" id="btn" />
#Html.RenderPartial("Partial", model)
Partial.cshtml
#model CustomModel
#Html.TextboxFor(x => x.lang.FirstOrDefault().id);
<input type="submit" id="submit" />
The thing is, when I click the submit button in the Partial.cshtml page, and examine the model in httppost method in public Action Partial(FormCollection frm, CustomModel model), the model contains null for both lists lstlang and lstOrg, but the formcollection[0] will give the selected textbox value.
What am I missing, or is this the right way of using partial views?

Don't use FirstOrDefault(). If you want to post something back to the front end with collections, you'll need to use indexing.
Public class CustomModel
{
public ICollection<lang> lstlang { get; set; }
public ICollection<org> lstOrg { get; set; }
}
#HTML.textboxfor(x=>x.lang[0].id);