MVC EF如何同时添加图像和其他数据库的值

我正在寻求在将图像（作为字节！）上传到数据库时的支持，同时还要上传其他属性。我必须承认，作为一个编程新手，我在完成这个任务时遇到了一些困难，但是我基本上搞定了。现在我的问题是，每当我尝试利用这个模型时，它就会停止工作，并弹出以下错误消息：

输入不是有效的Base-64字符串，因为它包含一个非Base-64字符，超过两个填充字符，或在填充字符中包含非法字符。

ViewModel：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.Entity;
using System.Data.Entity.ModelConfiguration.Conventions;
using System.ComponentModel.DataAnnotations;
namespace errandomWeb.Models
{
    public class PhotoCompetition
    {
        public int ID { get; set; }
        public string UserID { get; set; }
        public string FirstName { get; set; }
        public string Email { get; set; }
        public byte[] CompetitionPicture { get; set; }
        //[Required]
        [Display(Name = "通过勾选此框，我接受条款和条件")]
        //[CheckBoxRequired(ErrorMessage = "请接受我们的条款和条件参与活动。")]
        public bool TermsAndConditionsAccepted { get; set; }
        public DateTime TimeStamp { get; set; }
    }
}

View：

@model errandomWeb.Models.PhotoCompetition

Controller：

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.IO;
using System.Linq;
using System.Net;
using System.Threading.Tasks;
using System.Web;
using System.Web.Mvc;
using errandomWeb.Models;
using Microsoft.AspNet.Identity;
using Microsoft.AspNet.Identity.Owin;
namespace errandomWeb.Controllers
{
    [Authorize]
    public class errandomController : Controller
    {
        private ApplicationDbContext DB = new ApplicationDbContext();
        // GET: /errandom/PhotoCompetition
        public ActionResult PhotoCompetition()
        {
            var model = new PhotoCompetition
            {
                UserID = User.Identity.GetUserId(),
                Email = User.Identity.GetUserName(),
                FirstName = User.Identity.Name,
                TimeStamp = DateTime.UtcNow.ToUniversalTime()
            };
            return View(model);
        }
        // POST: /errandom/PhotoCompetition
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see https://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult UploadCompetitionPicture()
        {
            string croppedImage = Request.Form["photoCompetitionCroppedPicture"];
            byte[] imageBytes = Convert.FromBase64String(croppedImage.Split(',')[1]);
            var userId = User.Identity.GetUserId();
            var participation = new PhotoCompetition
            {
                CompetitionPicture = imageBytes,
                UserID = User.Identity.GetUserId(),
                FirstName = "testcase",
                Email = User.Identity.GetUserName(),
                TermsAndConditionsAccepted = false,
                TimeStamp = DateTime.UtcNow.ToUniversalTime(),
            };
            DB.PhotoCompetition.Add(participation);
            DB.SaveChanges();
            return View("Edit");
        }
    }
}

我想包含

TermsAndConditionsAccepted = model.TermsAndConditionsAccepted

所以该值实际上是从用户填写的表单中获取的，但由于上述原因，我遇到了问题。

非常感谢在这里得到的任何帮助，谢谢！