MVC Form submit not transferring the updated model back to action method for List

Question

My VIEW (success.cshtml) is as below

@model IList<AzSample.Models.Employeelist>    
@using (Html.BeginForm("Save","Home", FormMethod.Post))
{
    @Html.AntiForgeryToken()
    <h2>Employees Details</h2>
    <div>
        <table>
            <tr>
                <th>Id</th>
            </tr>
            @foreach (var emp in Model)
            {
                <tr>
                    <td>@emp.ID</td>
                </tr>
            }
        </table>
        <button type="submit" value="save"  onclick="@Url.Action("Save", "Home")">Save</button>
    </div>
}

My Home Controller is as below

public class HomeController : Controller
{
    public ActionResult Import(HttpPostedFileBase excelfile)
    {
        //Code to get data from Excel sheet
        List<Employeelist> obj = new List<Employeelist>();
        for( int row =2; row <=range.Rows.Count; row++)
        {
            Employeelist emp = new Employeelist();
            emp.ID =((Excel.Range)range.Cells[row,1]).Text;
            obj.Add(emp);
        }
        return View("success", obj);
    }

    [HttpPost]
    public ActionResult Save(List<Employeelist> empLIst)
    {
        // Code fro storing the data got from VIEW.
    }
}

My Model is as below

public class Employeelist
{
    public string ID { get; set; }
}

I am calling import action method from some other page, and reading the data from Excel sheet and showing it on success.cshtml. Till here it works fine.

When ever i click on Save button, the debug point is coming back to Save action method, but the data (i.e. List<Employeelist>, basically all Employeelist.ID's ) is null ? What is missing ?

Answer 1

The data for the empList is never submitted with the form. You should render <input> fields to submit your data.

 @for(int i = 0; i < Model.Count(); ++i) {
    @Html.HiddenFor(m => m[i].Id)
    // send other properties        
 }

It is important that you bind to indexed properties so the MVC modelbinder can bind this as a collection. @Html.HiddenFor(m => m.Id) will not work.

See also Model Binding to a List MVC 4

--Edit--

As Stephen has pointed out, the modelbinder will try to bind this using the index, so your c# model must implement IList<T>.

Another pitfall are non-sequential indices.

Answer 2

You should use this > ASP.NET MVC TempData ?

ASP.NET MVC TempData dictionary is used to share data between controller actions. The value of TempData persists until it is read or until the current user’s session times out. Persisting data in TempData is useful in scenarios such as redirection, when values are needed beyond a single request.

The code would be something like this:

---

Import Method:

public ActionResult Import(HttpPostedFileBase excelfile)
    {
        //Code to get data from Excel sheet
        for( int row =2; row <=range.Rows.Count; row++)
            {
                Employeelist emp = new Employeelist();
                emp.ID =((Excel.Range)range.Cells[row,1]).Text;
                obj.Add(emp);
            }
        TempData["doc"] = obj;
        return View("success", obj);
    }

View:

@model IEnumerable<AzSample.Models.Employeelist>    
@using (Html.BeginForm("Save","Home", FormMethod.Post))
{
@Html.AntiForgeryToken()
<h2>Employees Details</h2>
<div>
    <table>
        <tr>
            <th>Id</th>

        </tr>
 @{var list = (List<AzSample.Models.Employeelist>)TempData["doc"];}
@{TempData["doc"] = list;}
        @foreach (var emp in list)
        {
            <tr>
                <td>@emp.ID</td>
            </tr>
        }
    </table>

    <button type="submit" value="save"  onclick="@Url.Action("Save", "Home")">Save</button>
</div>
}

Save Method:

[HttpPost]
public ActionResult Save()
{
   if (TempData["doc"] != null)
    {
        // Your code will be here
    }
}