How to Properly Bind Dynamically Added Fields to a Model Using Html.BeginCollectionItem?

Partial View Passing Collection Using Html.BeginCollectionItem Helper

Problem

In a project utilizing the Html.BeginCollectionItem helper, new fields generated by JavaScript were not binding to the model during form submission. Additionally, the BeginCollectionItem helper did not render hidden tags for the new fields.

Solution

1. Create a View Model:

Define a view model (e.g., CashRecipientVM) to represent the data to be edited, with appropriate data annotations.

2. Create a Partial View:

Create a partial view (_Recipient.cshtml) using the BeginCollectionItem helper, including necessary labels, text boxes, and a delete button.

3. Implement a Method to Return the Partial View:

Implement a method in the controller to return the partial view (e.g., Recipient()).

4. Update GET Method:

In the main view's GET method, create an initial list of view models.

5. Update Main View:

In the main view, use a foreach loop to display the existing objects and add the partial view using the BeginCollectionItem helper.

6. Implement JavaScript for Adding Items:

Write JavaScript to add the HTML for a new view model to the form upon clicking a button.

7. Implement JavaScript for Deleting Items:

Write JavaScript to delete an item upon clicking the delete button, making an appropriate AJAX request to the server.

8. Update POST Method:

Update the form to post back to a method receiving a collection of the view models (e.g., Create(IEnumerable recipients)).

Additional Notes:

• Ensure the script to add items uses the correct URL for the Recipient method.
• Use data annotations to validate the data on the client side.
• To improve performance, consider using a knockout.js or MVVM framework instead of JavaScript for data binding.

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