I was able to limit the file size using Custom Fields. I followed the instruction in the documentation and I was able to limit using javascript. My Problem right now is when I change the input type to file from text I am getting a value of null. I am new to .Net so I'm no really sure what's wrong with my code. Please help.

FieldType.CustomField.cshtml

@model Umbraco.Forms.Web.Models.FieldViewModel

<input type="file" name="@Model.Name" id="@Model.Id" class="upload-resume" accept=".pdf, .doc, .docx"
@{
    if (string.IsNullOrEmpty(Model.PlaceholderText) == false)
    {
        <text> placeholder="@Model.PlaceholderText" </text>
    }
}
@{
    if (Model.Mandatory || Model.Validate)
    {
        <text> data-val="true" </text>
    }
}
@{
    if (Model.Mandatory)
    {
        <text> data-val-required="@Model.RequiredErrorMessage" </text>
    }
}
 />

<script>
    $(document).ready(function () {
        $('.upload-resume').on('change', function () {
            var input = this;

            if (input.files && input.files.length > 0) {

                var fileSize = input.files[0].size; // in bytes
                console.log(fileSize);


                var maxSize = 1024 * 1024; // 1MB


                if (fileSize > maxSize) {
                    alert("File size exceeds the allowed limit. Please choose a smaller file.");
                    $(input).val('');
                }
            }
        });
    });
</script>

CustomField.cs

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNetCore.Http;
using Umbraco.Forms.Core.Enums;
using Umbraco.Forms.Core.Models;
using Umbraco.Forms.Core.Services;

namespace MyGlobal.FormsExtensions.Fields
{
    public class CustomField : Umbraco.Forms.Core.FieldType
    {
        public CustomField()
        {
            Id = new Guid("08b8057f-06c9-4ca5-8a42-fd1fc2a46eff"); 
            Name = "Custom File Upload";
            Description = "Renders an upload field.";
            Icon = "icon-cloud-upload";
            DataType = FieldDataType.String;
            FieldTypeViewName = "FieldType.CustomField.cshtml";
        }

        // You can do custom validation in here which will occur when the form is submitted.
        // Any strings returned will cause the submission to be considered invalid.
        // Returning an empty collection of strings will indicate that it's valid to proceed.

        public override IEnumerable<string> ValidateField(Form form, Field field, IEnumerable<object> postedValues, HttpContext context, IPlaceholderParsingService placeholderParsingService, IFieldTypeStorage fieldTypeStorage)
        {
            var returnStrings = new List<string>();
            var file = postedValues.FirstOrDefault() as IFormFile;

            if (file == null)
            {
                returnStrings.Add("Please upload a file.");
            }
            else
            {
                // Add additional file-specific validation if needed
                // For example: Check file size, file type, etc.
                // Example: if (file.Length > maxSize) returnStrings.Add("File size exceeds the limit.");
            }

            // Validate against the default method
            return base.ValidateField(form, field, postedValues, context, placeholderParsingService, fieldTypeStorage);
        }
    }
}

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