How to Successfully POST a Form Array with ASP.NET MVC and jQuery?

Troubleshooting ASP.NET MVC Form Array Submission with jQuery

This article addresses a common problem: submitting a form array using ASP.NET MVC and jQuery, resulting in a null reference exception when attempting to access the array data in the controller. The issue typically arises when the form's array elements aren't properly indexed for correct model binding.

The scenario involves sending an IEnumerable<BatchProductViewModel> to the server. The solution requires generating form controls within a loop, ensuring each element is correctly named using indexers. Furthermore, the server-side model property (BatchProducts) should be an IList<BatchProductViewModel> to accommodate dynamic array sizes.

Here's a corrected code example demonstrating proper array handling:

@using (Html.BeginForm("Save", "ConnectBatchProduct", FormMethod.Post))
{
  // ... other form elements ...

  // Correctly indexed form elements for the array
  //  This loop ensures each element in the array has a unique index
  //  The indexer is crucial for proper model binding
  for (int i = 0; i < Model.BatchProducts.Count; i++)
  {
    @Html.HiddenFor(model => model.BatchProducts[i].ProductId) // Example property
    @Html.TextBoxFor(model => model.BatchProducts[i].ProductName) // Example property
    // ... other properties for BatchProductViewModel ...
  }

  // ... rest of the form ...

  <input type="submit" value="Save" />
}

With these adjustments, the Save action method in the ConnectBatchProduct controller will correctly receive a populated ConnectBatchProductViewModel object, including its BatchProducts list.

Dynamic Array Management (Add/Remove)

For dynamic addition and removal of BatchProductViewModel items using jQuery, consider employing the BeginCollectionItem helper or crafting a custom HTML template to manage the array elements efficiently. (Further details on these techniques can be found in [relevant online resources/links - replace bracketed information with actual links if available].)

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