Question

mvc如何异步检测文件类型和文件大小呢？

我用$.post()从后台获取Request.Files[uploadControlName]为null，为啥呢。应该怎么异步检测文件类型和大小呢？不需要上传，只要检测好了

Answer 1

文件你还是要上传的，存到内存里，不保存到物理硬盘就行。上传的［uploadControlName］为空，我想问的是你确定上传的表单类型是enctype="multipart/form-data"吗？

看看你$.post()里面是否有multipart/form-data类型的表单。

<form action="/File/UploadFile" method="post" enctype="multipart/form-data" >
     <input type="file" name="upload"  />
</form>

检测文件大小在内存里做，不保存就好，下面给你个例子，可以返回一个文本类型到界面。

public ActionResult UploadFile(string path)
        {
            try
            {
                //接受上传文件
                HttpPostedFileBase postFile = Request.Files["upload"];
                if (postFile != null)
                {
                    //获取上传目录 转换为物理路径
                    string uploadPath = Server.MapPath(path + "/");
                    //文件名
                    string fileName = postFile.FileName;
                    //获取文件大小
                    long contentLength = postFile.ContentLength;
                    //文件不能大于10M
                    if (contentLength <= 1024 * 10240)
                    {
                        //如果不存在path目录
                        if (!Directory.Exists(uploadPath))
                        {
                            //那么就创建它
                            Directory.CreateDirectory(uploadPath);
                        }
                        //保存文件的物理路径
                        string saveFile = uploadPath + fileName;
                        try
                        {
                            //保存文件
                            postFile.SaveAs(saveFile);
                        }
                        catch
                        {
                            ;
                        }

                    }
                    else
                    {
                        //文件大小超过10MB";
                    }
                }
                else
                {
                    //"文件大小超过10MB";
                }
            }
            catch (Exception e)
            {
                //"上传文件失败";
            }
            return Redirect(Request.UrlReferrer.AbsoluteUri);
        }