What is the difference between "Value" and "Name" in input hidden element?

Question

Hello,

I have two questions.

1- What is the difference between "Value" and "Name" in the input hidden element? And what do they do?

2- What is the Index and what does it refer to? I don't have an Index property or method in my model/page model. When I change the name of the word Index, the program does not work! name="Inputs.Index"

Thanks in advance

namespace CityBreaks.Models
{
    public class Country
    {
        public int Id { get; set; }
        public string CountryName { get; set; }
        public string CountryCode { get; set; }
    }

}

using CityBreaks.Models;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace CityBreaks.Pages.CountryManager
{
    public class EditModel : PageModel
    {
        [BindProperty]
        public List<InputModel> Inputs { get; set; }
        public List<Country> Countries { get; set; } = new List<Country>();
        public void OnGet()
        {
               
            Inputs = new List<InputModel> {
                new InputModel{ Id = 840, CountryCode = "us", CountryName ="United States" },
                new InputModel{ Id = 826, CountryCode = "en", CountryName = "Great Britain" },
                new InputModel{ Id = 250, CountryCode = "fr", CountryName = "France" }
            };
        }

        public void OnPost()
        {
            Countries = Inputs
                .Where(x => !string.IsNullOrWhiteSpace(x.CountryCode))
                .Select(x => new Country
                {
                    Id = x.Id,
                    CountryCode = x.CountryCode,
                    CountryName = x.CountryName
                }).ToList();
        }

        public class InputModel
        {
            public int Id { get; set; }
            public string CountryName { get; set; }
            public string CountryCode { get; set; }

        }
    }
}

@page
@model CityBreaks.Pages.CountryManager.EditModel
@{
}
<h4>Edit Countries</h4>

<div class="row">
    <div class="col-md-8">
        <form method="post">
            <table class="table table-borderless">
                <tr>
                    <th>Name</th>
                    <th>ISO-3166-1 Code</th>
                </tr>
                @foreach (var country in Model.Inputs)
                {
                         <input type="hidden" name="Inputs.Index" value="@country.Id" /> // HERE
                    <tr>
                        <td class="w-75">
                       <input name="Inputs[@country.Id].CountryName" 
                                          value="@country.CountryName" 
                            class="form-control" />
                    </td>
                        <td class="w-25">
                        <input name="Inputs[@country.Id].CountryCode" 
                            value="@country.CountryCode" 
                            class="form-control" />
                    </td>
                    </tr>
                }
            </table>
            <div class="form-group">
                <input type="submit" value="Update" class="btn btn-primary" />
            </div>
        </form>
    </div>
</div>
@if (Model.Countries.Any())
{
    <p>You submitted the following</p>
    <ul>
    @foreach (var country in Model.Countries)
    {
        <li>
            <img src="/images/flags/@(country.CountryCode).png" />
            @country.CountryName
        </li>
    }
    </ul>
}

Answer 1

First of all:

• Value: The "value" attribute is used to specify the data that will be sent to the server when the form is submitted. It represents the value of the hidden input element. For example, <input type="hidden" name="user_id" value="123"> will send the value "123" as "user_id" to the server when the form is submitted. The user does not see this value, as the input is hidden.
• Name: The "name" attribute is used to define the input element's name, which is used as a reference when the form is submitted to the server. It represents the key or identifier under which the value will be sent to the server. For example, <input type="hidden" name="user_id" value="123"> will send "user_id=123" to the server when the form is submitted. The "name" attribute is essential for server-side processing of form data.

https://www.w3schools.com/tags/att_name.asp

And the "Index" you see in the name attribute (name="Inputs.Index") is related to the behaviour of form elements when used within a list or collection in a Razor view in ASP.NET Core. The Razor view engine uses the "Index" value to ensure proper model binding and correctly handle collections of form elements.