ASP.NET MVC 文件上传和文件下载

@model System.Web.HttpContextBase
@{
    ViewBag.Title = "上传文件";
}
<h2>上传文件</h2>
<br />
<br />
@*new { enctype = "multipart/form-data" }比不可少，否则上传文件不会成功 *@
@using (Html.BeginForm("Upload", "UploadFile", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
    <text>选择上传文件：</text><input name="file" type="file" id="file" />
    <br />
    <br />
    <input type="submit" name="Upload" value="Upload" />
}

[HttpPost]
        public ActionResult Upload(FormCollection form)
        {
            if (Request.Files.Count == 0){
                //Request.Files.Count 文件数为0上传不成功
                return View();
            }
            var file = Request.Files[0];
            if (file.ContentLength == 0){
                //文件大小大（以字节为单位）为0时，做一些操作
                return View();
            }
            else{
                //文件大小不为0
                file = Request.Files[0];
                //保存成自己的文件全路径,newfile就是你上传后保存的文件,
                //服务器上的UpLoadFile文件夹必须有读写权限
                string target = Server.MapPath("/")+("/Mock/Learning/");//取得目标文件夹的路径
                string filename = file.FileName;//取得文件名字
                string path = target + filename;//获取存储的目标地址
                file.SaveAs(path);}
            return View();
        }

<a href="/DownloadFile/Download?filePath=@ViewBag.Value&fileName=‘小王子.pdf‘">下载</a>

public ActionResult Download(string filePath, string fileName)
        {
            Encoding encoding;
            string outputFileName = null;
            fileName = fileName.Replace("‘", "");
            
            string browser =Request.UserAgent.ToUpper();
            if (browser.Contains("MS") == true && browser.Contains("IE") == true)
            {
                outputFileName = HttpUtility.UrlEncode(fileName);
                encoding =Encoding.Default;
            }
            else if (browser.Contains("FIREFOX") == true)
            {
                outputFileName = fileName;
                encoding =Encoding.GetEncoding("GB2312");
            }
            else
            {
                outputFileName = HttpUtility.UrlEncode(fileName);
                encoding = Encoding.Default;
            }
            FileStream fs = new FileStream(filePath, FileMode.Open);
            byte[] bytes = new byte[(int)fs.Length];
            fs.Read(bytes, 0, bytes.Length);
            fs.Close();
            Response.Charset = "UTF-8";
            Response.ContentType = "application/octet-stream";
            Response.ContentEncoding = encoding;
            Response.AddHeader("Content-Disposition", "attachment; filename=" + outputFileName);
            Response.BinaryWrite(bytes);
            Response.Flush();
            Response.End();
            return new EmptyResult();
        }