modelstate error 'The Id field is required' in mvc4 application - asp.net-mvc

Question

I m using a viewmodel on my create view. Every thing works but on form post via jquery I m getting The Id field is required ModelState error. I have seen some solutions regarding adding [Bind(Exclude = "Id")] annotation in the model class but then when I call the same action method on the Update model it never binds the Id of the model and inserts a new record in db.
My viewmodel looks like
public class MemberSiteContactModel
{
public int Id { get; set; }
[Display(Name = "Name")]
[Required(ErrorMessage = "Name is required")]
public string Name { get; set; }
// More items
}
My partial view looks like
#model MemberSiteContactModel
<tr class="highlight">
<td class="col-sm-1">#Html.TextBoxFor(x => x.Name, new { #class = "name" })</td>
<td class="col-sm-2">#Html.TextBoxFor(x => x.ContactNo, new { #class = "contactNo" })</td>
<td class="col-sm-1"><input type="button" class="btn btn-xs btn-success contactSaveRow" value="Save" /></td>
<td class="col-sm-1"><input type="button" class="btn btn-xs btn-danger contactDeleteRow" value="Remove" name="btnRemoveContact" /></td>
</tr>
My controller looks like
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult SaveSiteContact(MemberSiteContactModel memberSiteContactModel)
{
if (ModelState.IsValid)
{
//processing
}
}
I have also created a sample application to replicate the behavior
public class CityModel
{
public int Id { get; set; }
[Display(Name = "City")]
[Required(ErrorMessage = "City is required")]
public string City { get; set; }
}
public ActionResult Contact()
{
return View();
}
#model WebApplication3.Models.CityModel
#using (#Html.BeginForm("SaveCity", "Home", FormMethod.Post))
{
#Html.HiddenFor(x => x.Id)
#Html.TextBoxFor(x => x.City)
<input type="submit" value="Submit" />
}
[HttpPost]
public ActionResult SaveCity(CityModel cityModel)
{
if (ModelState.IsValid)
{
}
return null;
}

Answer 1

You're not passing the Id in, you need to add a hidden field that holds to Id otherwise how does the Id ever get passed into the posted model.
#Html.HiddenFor(x => x.Id)

Answer 2

I'm using MVC and have the same problem, so i check out all my create code and find that i wasn't send an empty model to the View at call time. The solution was simple; on the Create() action result, just add a line that creates a new ViewModel and set it as parameter to the View or Partial View return. Something like this:
public ActionResult Create(){
ViewModel entity = new ViewModel();
return PartialView(entity);
}
I hope that helps.