.netCore上传图片，要用FormFileCollection ,不能用List

   [HttpPost]
        //[ValidateInput(false)]
        public IActionResult AddProInfo(ProductInfo productInfo, IFormFileCollection ProductImg)
        {
            ///获取富文本
            productInfo.ProductRemark = FuWenBen;

            //获取品牌
            //productInfo.ProductBrand = Session["ProductBrand"].ToString();

            //获取分类
            //productInfo.ProductType = Session["prop"].ToString();
            #region 非空判断
            //if (string.IsNullOrWhiteSpace(productInfo.ProductImg))
            //{
            // Response.WriteAsync("<script>alert('请上传图片！');location.href='/ProductInfos/AddProInfo'</script>",Encoding.GetEncoding("GB2312"));
            //}
            if (string.IsNullOrWhiteSpace(productInfo.ProductName))
            {
                Response.WriteAsync("<script>alert('请填写名称！');location.href='/ProductInfos/AddProInfo'</script>", Encoding.GetEncoding("GB2312"));
            }
            if (string.IsNullOrWhiteSpace(productInfo.ProductNum))
            {
                Response.WriteAsync("<script>alert('请添加商品货号！');location.href='/ProductInfos/AddProInfo'</script>", Encoding.GetEncoding("GB2312"));
            }
            if (string.IsNullOrWhiteSpace(productInfo.ProductCount.ToString()) || productInfo.ProductCount == 0)
            {
                Response.WriteAsync("<script>alert('请添加库存！');location.href='/ProductInfos/AddProInfo'</script>", Encoding.GetEncoding("GB2312"));
            }
            if (string.IsNullOrWhiteSpace(productInfo.ProductFlag))
            {
                Response.WriteAsync("<script>alert('请选择商品属性！');location.href='/ProductInfos/AddProInfo'</script>", Encoding.GetEncoding("GB2312"));
            }
            if (string.IsNullOrWhiteSpace(productInfo.ProductPrice.ToString()) || productInfo.ProductPrice == 0)
            {
                Response.WriteAsync("<script>alert('请填写商品价格！');location.href='/ProductInfos/AddProInfo'</script>", Encoding.GetEncoding("GB2312"));
            }
            if (!ModelState.IsValid)
            {
                Response.WriteAsync("<script>alert('请填写库存！');location.href='/ProductInfos/AddProInfo'</script>", Encoding.GetEncoding("GB2312"));
            }
            #endregion

            try
            {
                //productInfo.ProductBrand = Session["ProductBrand"].ToString();
                //productInfo.ProductType = Session["prop"].ToString();



                //上架状态
                productInfo.ProductState = 1;
                StringBuilder builder = new StringBuilder();
                foreach (var item in ProductImg)
                {
                    string fileName = item.FileName;
                    var path = hostingEnvironment.WebRootPath + "/Image/" + fileName;
                    builder.Append("/Image/").Append(fileName).Append(",");
                    //using (FileStream fileStream=System.IO.File.Create(path))
                    //{
                    // item.CopyTo(fileStream);
                    // fileStream.Flush();
                    //}
                    using (var stream = System.IO.File.Create(path))
                    {
                        item.CopyToAsync(stream);
                    }
                }
                productInfo.ProductImg = builder.ToString();
                if (bll.AddData(productInfo) > 0)
                {
                    Response.WriteAsync("<script>alert('添加成功');location.href='/ProductInfos/ShowProduct';</script>", Encoding.GetEncoding("GB2312"));
                }
                else
                {
                    Response.WriteAsync("<script>alert('添加失败');</script>", Encoding.GetEncoding("GB2312"));
                }
            }
            catch (Exception e)
            {
                Response.WriteAsync("<script>alert('请选择品牌和分类');location.href='/ProductInfos/AddProInfo'</script>", Encoding.GetEncoding("GB2312"));
            }

            return View();
        }