using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using JYRS.Util;
namespace JYRS.Utils
{
  public class FileHelper
  {
    /// <summary>
    /// 将文件名解析成文件的上传路径
    /// </summary>
    /// <param name="fileName">文件名</param>
    /// <param name="path">文件路径</param>
    /// <returns path>文件在服务器上的路径</returns>
    public static String transPath(string fileName, string path)
    {
      createDir(path)；
      //取服务器时间+8位随机码作为部分文件名，确保文件名无重复
      string nowStr = DateTime.Now.ToString("yyyyMMddhhmmssff") + Global.CreateRandomCode(8);
      // 去掉后缀的文件名
      string fileNameStr = fileName.Substring(0, fileName.LastIndexOf("."));
      // 文件后缀
      String suffix = fileName.Substring(fileName.LastIndexOf(".") + 1);
      if (fileName.Trim() != "")
      {
        // 如果名称不为"",说明该文件存在，否则说明该文件不存在
        path += "\\" + fileNameStr + nowStr + "." + suffix;// 定义上传路径
      }
      return path;
    }
    /// <summary>
    /// 创建文件目录
    /// </summary>
    /// <param name="root">根目录</param>
    /// <returns ></returns>
    private static void createDir(String root)
    {
      // 检查目录
      if (!Directory.Exists(System.Web.HttpContext.Current.Server.MapPath(root)))
      {
        Directory.CreateDirectory(System.Web.HttpContext.Current.Server.MapPath(root));
      }
    }
    /// <summary>
    /// 根据文件在服务器上的路径下载文件，此处采用的是WebAPI的方式进行文件下载，下载成功后可自定义文件的保存路径
    /// </summary>
    /// <param name="fileName">文件名</param>
    /// <param name="path">文件路径</param>
    /// <returns></returns>
    public static HttpResponseMessage download(string fileName, string path)
    {
      try
      {
        var stream = new FileStream(path, FileMode.Open);
        HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
        response.Content = new StreamContent(stream);
        response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
        response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
        {
          FileName = fileName
        };
        return response;
      }
      catch
      {
        return new HttpResponseMessage(HttpStatusCode.NoContent);
      }
    }
  }
}

[HttpGet]
public HttpResponseMessage UploadAndDownload()
{
  //文件上传到服务器上的根目录
  string root = System.Web.Hosting.HostingEnvironment.MapPath(@"~/upload");
  string fileName = "测试.docx";
  //解析文件在服务器上的上传路径
  string path = FileHelper.transPath(fileName, root);
  //获取要上传的文件
  var files = HttpContext.Current.Request.Files;
  HttpPostedFile file = HttpContext.Current.Request.Files[0];
  //保存文件
  file.SaveAs(System.Web.HttpContext.Current.Server.MapPath(path));
  //下载word文件
  return FileHelper.download(fileName, path);
}

<a href="http://localhost:60179/api/CeshiController/UploadAndDownload" rel="external nofollow" "> 导出 </a>