How to add ModelState.AddModelError message when model item is not binded

Question

I am new to MVC4. Here I added the ModelState.AddModelError message to display when the delete operation is not possible.

  <td>     <a id="aaa" href="@Url.Action("Delete", "Shopping", new { id = Request.QueryString["UserID"], productid = item.ProductID })" style="text-decoration:none">     <img alt="removeitem" style="vertical-align: middle;" height="17px" src="~/Images/remove.png"  title="remove" id="imgRemove" />       </a>       @Html.ValidationMessage("CustomError")     </td>      @Html.ValidationSummary(true) 

In my controller

public ActionResult Delete(string id, string productid)         {                          int records = DeleteItem(id,productid);             if (records > 0)             {               ModelState.AddModelError("CustomError", "The item is removed from your cart");                return RedirectToAction("Index1", "Shopping");             }             else             {                 ModelState.AddModelError(string.Empty,"The item cannot be removed");                 return View("Index1");             }         } 

Here I didnt pass any of the model item in the View to check for the item in Model and I couldnt get the ModelState error message ..
Any suggestions

Answer 1

The ModelState is created at each request so you should use TempData.

public ActionResult Delete(string id, string productid) {                  int records = DeleteItem(id,productid);     if (records > 0)     {             // since you are redirecting store the error message in TempData         TempData["CustomError"] = "The item is removed from your cart";         return RedirectToAction("Index1", "Shopping");     }     else     {         ModelState.AddModelError(string.Empty,"The item cannot be removed");         return View("Index1");     } }  public ActionResult Index1() {     // check if TempData contains some error message and if yes add to the model state.     if(TempData["CustomError"] != null)     {         ModelState.AddModelError(string.Empty, TempData["CustomError"].ToString());     }      return View(); } 

Answer 2

RedirectToAction will clear ModelState. You must return a view in order to use this data. Therefore, the first if case won't work. Also, ensure that you have a control in your view (like ValidationSummary) which displays the error... this could be the problem in the second case.