How do I add a watermark to multiple images using bitmap

using System.Web.Mvc;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;

namespace something.Controllers
{

    public class something: Controller
    {
        public ActionResult Index()
        {
            return View();
        }

        [HttpPost]
        public ActionResult Index(string text, string text1)
        {
            DirectoryInfo dir = new DirectoryInfo(@"C:\Users\name\Desktop\Images");
            FileInfo[] files = dir.GetFiles();
            string value = text;
            string value1 = text1;
            foreach (FileInfo file in files)
            {
          

                using (Bitmap bitmap = new Bitmap( file.FullName))
                {
                    using (Graphics graphics = Graphics.FromImage(bitmap))
                    {
                        Brush brush = new SolidBrush(Color.Red);
                        Font font = new Font("Arial", 10, FontStyle.Italic, 
                        GraphicsUnit.Pixel);
                        SizeF textSize = new SizeF();
                        textSize = graphics.MeasureString(value, font);
                        Point position = new Point(bitmap.Width - ((int)textSize.Width + 
                        30), bitmap.Height - ((int)textSize.Height + 10));
                        graphics.DrawString((value + value1), font, brush, position);
                        using (MemoryStream mStream = new MemoryStream())
                        {
                            mStream.Position = 0;
                            bitmap.Save(mStream, ImageFormat.Png);
                           


                            string _path = 
                            Path.Combine(Server.MapPath("~/UploadedFolders"), 
                            file.Name);
                            bitmap.Save(_path);
                            return File(mStream.ToArray(), "image/png", file.Name);
                        }
                    }
                }



            }
            return View();
        }

    }

}

@model something.something

@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>UploadFile</h2>

@{
    ViewBag.Title = "UploadFile";
}


@using (Html.BeginForm("Index", "something", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
    @Html.AntiForgeryToken()



    <div class="form-group">
        @Html.LabelFor(m => m.preFix)
        
        <input type="text" class="form-control" required name="text" id="preFix" />
    </div>
    <div class="form-group">
        @Html.LabelFor(m => m.pageNumber)

        <input type="text" class="form-control" required name="text1" id="pageNumber" />
    </div>
 


    <input type="submit" class="btn btn-info" value="Upload" />

    @ViewBag.Message




}

Bitmap picture = new Bitmap(@"C:\Users\Desktop\A\" + file.FullName + ".bmp");