Submit same Partial View called multiple times data to controller?

Question

Your problem is that the partial renders html based on a single AdminProductDetailModel object, yet you are trying to post back a collection. When you dynamically add a new object you continue to add duplicate controls that look like <input name="productTotalQuantity" ..> (this is also creating invalid html because of the duplicate id attributes) where as they need to be <input name="[0].productTotalQuantity" ..>, <input name="[1].productTotalQuantity" ..> etc. in order to bind to a collection on post back.

The DefaultModelBinder required that the indexer for collection items start at zero and be consecutive, or that the form values include a Index=someValue where the indexer is someValue (for example <input name="[ABC].productTotalQuantity" ..><input name="Index" value="ABC">. This is explained in detail in Phil Haack's article Model Binding To A List. Using the Index approach is generally better because it also allows you to delete items from the list (otherwise it would be necessary to rename all existing controls so the indexer is consecutive).

Two possible approaches to your issue.

Option 1

Use the BeginItemCollection helper for your partial view. This helper will render a hidden input for the Index value based on a GUID. You need this in both the partial view and the loop where you render existing items. Your partial would look something like

@model IKLE.Model.ProductModel.AdminProductDetailModel
@using(Html.BeginCollectionItem()) 
{
  <div class="editor-field">
    @Html.LabelFor(model => model.fkConfigChoiceCategorySizeId)
    @Html.DropDownListFor(model => model.fkConfigChoiceCategorySizeId, Model.sizeList, "--Select Size--")
    @Html.ValidationMessageFor(model => model.fkConfigChoiceCategorySizeId)
  </div>
  ....
}

Option 2

Manually create the html elements representing a new object with a 'fake' indexer, place them in a hidden container, then in the Add button event, clone the html, update the indexers and Index value and append the cloned elements to the DOM. To make sure the html is correct, create one default object in a for loop and inspect the html it generates. An example of this approach is shown in this answer

<div id="newItem" style="display:none">

  <div class="editor-field">
    <label for="_#__productTotalQuantity">Quantity</label>
    <input type="text" id="_#__productTotalQuantity" name="[#].productTotalQuantity" value />
    ....
  </div>
  // more properties of your model
</div>

Note the use of a 'fake' indexer to prevent this one being bound on post back ('#' and '%' wont match up so they are ignored by the DefaultModelBinder)

$('#addField').click(function() {
  var index = (new Date()).getTime(); 
  var clone = $('#NewItem').clone();
  // Update the indexer and Index value of the clone
  clone.html($(clone).html().replace(/\[#\]/g, '[' + index + ']'));
  clone.html($(clone).html().replace(/"%"/g, '"' + index  + '"'));
  $('#yourContainer').append(clone.html());
}

The advantage of option 1 is that you are strongly typing the view to your model, but it means making a call to the server each time you add a new item. The advantage of option 2 is that its all done client side, but if you make any changes to you model (e.g. add a validation attribute to a property) then you also need to manually update the html, making maintenance a bit harder.

Finally, if you are using client side validation (jquery-validate-unobtrusive.js), then you need re-parse the validator each time you add new elements to the DOM as explained in this answer.

$('form').data('validator', null);
$.validator.unobtrusive.parse($('form'));

And of course you need to change you POST method to accept a collection

[HttpPost]
public ActionResult AddDetail(IEnumerable<AdminProductDetailModel> model)
{
  ....
}