My goal is to return a .CSV file which contains Persian text characters from an ASP.NET Core 8.0 Web API controller action method as a FileContentResult.

I tried the suggested attempts which led me no where.

using Microsoft.AspNetCore.Mvc;
using System.Text;

namespace WebApplication.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class TestController : ControllerBase
    {

        [HttpGet("attempt1")]
        public IActionResult GetCsv()
        {
            // Sample data with Persian characters
            var csvData = "لورم ایپسوم متن ساختگی با تولید سادگی نامفهوم از صنعت چاپ، و با استفاده از طراحان گرافیک است .";

            Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
            // Get Windows-1256 encoding
            var encoding = Encoding.GetEncoding("windows-1256");

            // Encode CSV data in Windows-1256
            var bytes = encoding.GetBytes(csvData);

            // Return the CSV file with proper encoding
            return File(bytes, "text/csv", "persian.csv");
        }

        [HttpGet("attempt2")]
        public IActionResult GetCsv2()
        {
            var csvData = "لورم ایپسوم متن ساختگی با تولید سادگی نامفهوم از صنعت چاپ، و با استفاده از طراحان گرافیک است .";

            Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
            var encoding = Encoding.GetEncoding(1256);

            var bytes = encoding.GetBytes(csvData);

            return File(bytes, "text/csv", "persian.csv");
        }

        [HttpGet("attempt3")]
        public IActionResult GetCsv3()
        {
            var csvData = "لورم ایپسوم متن ساختگی با تولید سادگی نامفهوم از صنعت چاپ، و با استفاده از طراحان گرافیک است .";


            Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
            var encoding = Encoding.GetEncoding("windows-1256");

            var bytes = encoding.GetBytes(csvData);

            // Set the content type and charset in the response headers
            Response.Headers.Add("Content-Disposition", "attachment; filename=persian.csv");
            Response.ContentType = "text/csv; charset=windows-1256";

            return File(bytes, "text/csv", "persian.csv");
        }

        [HttpGet("attempt4")]
        public IActionResult GetCsv4()
        {
            // Sample data with Persian characters
            var csvData = "لورم ایپسوم متن ساختگی با تولید سادگی نامفهوم از صنعت چاپ، و با استفاده از طراحان گرافیک است .";

            Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
            var destEncoding = Encoding.GetEncoding("windows-1256");

            var bytes = Encoding.Convert(Encoding.UTF8, destEncoding, Encoding.UTF8.GetBytes(csvData));

            return File(bytes, "text/csv", "persian.csv");
        }

        [HttpGet("attempt5")]
        public IActionResult GetCsv5()
        {
            var csvData = "لورم ایپسوم متن ساختگی با تولید سادگی نامفهوم از صنعت چاپ، و با استفاده از طراحان گرافیک است .";

            Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
            var encoding = Encoding.GetEncoding("windows-1256");
            
            // Encode CSV data in Windows-1256 with BOM (if needed)
            var preamble = encoding.GetPreamble(); // Normally, Windows-1256 does not use a BOM, so this will be empty
            var bytes = encoding.GetBytes(csvData);

            // Combine preamble and byte data (normally preamble is empty for Windows-1256)
            var fileContent = new byte[preamble.Length + bytes.Length];
            System.Buffer.BlockCopy(preamble, 0, fileContent, 0, preamble.Length);
            System.Buffer.BlockCopy(bytes, 0, fileContent, preamble.Length, bytes.Length);

            // Return the CSV file with proper encoding
            return File(fileContent, "text/csv", "persian.csv");
        } 
    }
}

None of the actions return a .CSV file with readable text, they provide content which illegible text only:

Also if I open the file as “Notepad++” the encoding is set to UTF-8 and not to “Windows-1256” which is my goal:

Info: I’m using .NET 8.0 on Windows 10 OS.