Error Loading and Deleting Images using HTML Input File Control

protected void btnUploadImgPicture1_ServerClick(object sender, EventArgs e)
        {
            using (filePicture1)
            {
                if (filePicture1.PostedFile.FileName != "")
                {
                    imageUtil = new ImageUtility();
                    string realPhysicalPath = Path.Combine(Server.MapPath("~/upload/"), filePicture1.PostedFile.FileName);
                    filePicture1.PostedFile.SaveAs(realPhysicalPath);
                    //imgVehiclePicture1.Src = realPhysicalPath;
                    using (imgVehiclePicture1)
                    {
                        imgVehiclePicture1.Attributes["src"] = imageUtil.getBase64String(realPhysicalPath);
                        Session.Add("Image1", realPhysicalPath);
                        imageUtil = null;
                    }

                }
            }
        }

public  string getBase64String(string path)
        {
            Image img = Image.FromFile(path);
            byte[] imageBytes = imageToByteArray(img);
            string base64String = Convert.ToBase64String(imageBytes, 0, imageBytes.Length);
            return "data:image/png;base64," + base64String;
        }