Query string param is missed when form validation fail

Question

I have an form with following url: CreateEntity?officeCodeId=5

When I send form to validate and if validation is fail it returns just CreateEntity u

Answer 1

Your actions should looks like this:

Actions:

[HttpGet]
public virtual ActionResult CreateEntity(int? officeCodeId)
{            
    var model = new CreateViewModel();
    FillViewModel(model, officeCodeId);
    return View("Create", model);
}

[HttpPost]
public virtual ActionResult CreateEntity(ViewModel model)
{            
    if (model.IsValid) {
       // save...
       return RedirectToAction("EditEntity", newId!!!);
    } 

    return View("Create", model);
}

Html:

 @using (Html.BeginForm()) {
     @Html.HiddenFieldFor(m => Model.officeCodeId)
     ...
 } 

Your officeId should be in model. And on html form you can store it in hidden field.

Answer 2

Your final answer is excellent and works great, although you can further enhance it to make it more generic by simply including Request.QueryString:

<form action="@Url.Action("CreateEntity", "Employee")?@(Request.QueryString)"
  enctype="multipart/form-data" method="POST">

Then use the POST action:

[HttpPost]
protected virtual ActionResult CreateEntity(TEditViewModel model)
{
    if (!ModelState.IsValid)
    {
        return View(model);
    }

Answer 3

The problem is your HttpPost action doesn't have any notion of an id parameter. If you want to support a similar URL then make the action signature support that parameter e.g.

[HttpGet]
public ActionResult CreateEntity(int? officeCodeId)

[HttpPost]
public ActionResult CreateEntity(int officeCodeId, EditViewModel model);