วิธีการเพิ่มลายน้ำในเอกสาร Word ผ่าน ASP.NET Core REST API

using System.IO;
using System.Threading.Tasks;
using Aspose.Words;
using Aspose.Words.Drawing;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;

namespace WatermarkAPI.Controllers
{
    [ApiController]
    [Route("api/[controller]")]
    public class WatermarkController : ControllerBase
    {
        [HttpPost("add-watermark")]
        public async Task<IActionResult> AddWatermark(IFormFile file, [FromQuery] string watermarkText)
        {
            if (file == null || file.Length == 0 || string.IsNullOrWhiteSpace(watermarkText))
                return BadRequest("กรุณาอัปโหลดเอกสาร Word ที่ถูกต้องและระบุข้อความลายน้ำ");

            try
            {
                var tempFilePath = Path.GetTempFileName();
                using (var stream = new FileStream(tempFilePath, FileMode.Create))
                {
                    await file.CopyToAsync(stream);
                }

                Document doc = new Document(tempFilePath);
                AddTextWatermark(doc, watermarkText);

                var outputStream = new MemoryStream();
                doc.Save(outputStream, SaveFormat.Docx);

                outputStream.Position = 0;
                return File(outputStream, "application/vnd.openxmlformats-officedocument.wordprocessingml.document", "watermarked.docx");
            }
            catch (System.Exception ex)
            {
                return StatusCode(500, $"ข้อผิดพลาดภายในเซิร์ฟเวอร์: {ex.Message}");
            }
        }

        private void AddTextWatermark(Document doc, string text)
        {
            foreach (Section section in doc.Sections)
            {
                var watermark = new Shape(doc, ShapeType.TextPlainText)
                {
                    TextPath = { Text = text, FontFamily = "Arial" },
                    Width = 300,
                    Height = 70,
                    Rotation = -40,
                    FillColor = System.Drawing.Color.LightGray,
                    StrokeColor = System.Drawing.Color.LightGray,
                    WrapType = WrapType.None,
                    BehindText = true,
                    RelativeHorizontalPosition = RelativeHorizontalPosition.Page,
                    RelativeVerticalPosition = RelativeVerticalPosition.Page,
                    Left = 100,
                    Top = 200
                };

                section.HeadersFooters[HeaderFooterType.HeaderPrimary]?.AppendChild(watermark);
            }
        }
    }
}