public ActionResult CheckFullFile()
{
    try
    {
        var md5 = Convert.ToString(Request["md5"]);
        var ext = Convert.ToString(Request["ext"]);
        var size = Convert.ToInt64(Request["size"]);

        var fileName = md5 + "." + ext;
        var filePath = Server.MapPath(FilesDir) + "/" + fileName;//当前文件目录

        FileInfo file = new FileInfo(filePath);
        if (!file.Exists)
        {
            var chunkNums = 0;
            var chunkPath = Server.MapPath(ChunksDir + "/" + md5);//当前分片文件目录
            if (Directory.Exists(chunkPath))
            {
                DirectoryInfo dicInfo = new DirectoryInfo(chunkPath);
                var files = dicInfo.GetFiles();
                chunkNums = files.Count();
                if (chunkNums > 1)
                {
                    chunkNums = chunkNums - 1; //当文件上传中时，页面刷新，上传中断，这时最后一个保存的块的大小可能会有异常，所以这里直接删除最后一个块文件
                }
            }
            return Json(new { ifExist = file.Exists, chunkNums }, JsonRequestBehavior.AllowGet);
        }
        else
        {
            return Json(new { ifExist = file.Exists }, JsonRequestBehavior.AllowGet);
        }


    }
    catch (Exception e)
    {
        return Json(new { ifExist = false }, JsonRequestBehavior.AllowGet);
    }
} 

public ActionResult Upload(HttpPostedFileBase file)
{
    if (file != null)
    {
        string md5 = Request["md5"];
        //如果进行了分片
        if (Request.Form.AllKeys.Any(m => m == "chunk"))
        {
            int chunk = Convert.ToInt32(Request.Form["chunk"]);//当前分片在上传分片中的顺序（从0开始）
            string chunkDir = Server.MapPath(ChunksDir + "/" + md5);//当前分片文件目录
            string chunkPath = chunkDir + "/" + chunk;//分片文件路径

            //建立临时传输文件夹
            if (!Directory.Exists(chunkDir))
            {
                Directory.CreateDirectory(chunkDir);
            }
            file.SaveAs(chunkPath);
            return Json(new { isUpload = true, ext = Path.GetExtension(file.FileName) }, JsonRequestBehavior.AllowGet);
        }
        else//没有分片直接保存
        {
            var fileDir = Server.MapPath(FilesDir) + "/" + md5;
            string filePath = fileDir + Path.GetExtension(Request.Files[0].FileName);
            file.SaveAs(filePath);
            return Json(new { isUpload = true, savePath = filePath }, JsonRequestBehavior.AllowGet);
        }
    }
    else
    {
        return Json(new { isUpload = false }, JsonRequestBehavior.AllowGet);
    }
}

public ActionResult MergeFiles()
{
    string md5 = Request["md5"];
    string ext = Request["ext"];
    var fileName = md5 + "." + ext;
    string sourcePath = Server.MapPath(ChunksDir + "/" + md5);//源数据文件夹
    string targetFilePath = Server.MapPath(FilesDir) + "/" + fileName; //合并后的文件

    if (!Directory.Exists(Server.MapPath(FilesDir)))
    {
        Directory.CreateDirectory(Server.MapPath(FilesDir));
    }
    if (Directory.Exists(sourcePath))
    {
        DirectoryInfo dicInfo = new DirectoryInfo(sourcePath);
        FileInfo[] files = dicInfo.GetFiles();
        foreach (FileInfo file in files.OrderBy(f => int.Parse(f.Name)))
        {
            FileStream addFile = new FileStream(targetFilePath, FileMode.Append, FileAccess.Write);
            BinaryWriter AddWriter = new BinaryWriter(addFile);

            //获得上传的分片数据流 
            Stream stream = file.Open(FileMode.Open);
            BinaryReader TempReader = new BinaryReader(stream);
            //将上传的分片追加到临时文件末尾
            AddWriter.Write(TempReader.ReadBytes((int)stream.Length));
            //关闭BinaryReader文件阅读器
            TempReader.Close();
            stream.Close();
            AddWriter.Close();
            addFile.Close();

            TempReader.Dispose();
            stream.Dispose();
            AddWriter.Dispose();
            addFile.Dispose();
        }
        DeleteFolder(sourcePath);
        return Json(new { isMerge = true, savePath = HttpUtility.UrlEncode(targetFilePath) }, JsonRequestBehavior.AllowGet);
    }
    else
    {
        return Json(new { isMerge = false, savePath = HttpUtility.UrlEncode(targetFilePath) }, JsonRequestBehavior.AllowGet);
    }
}
private void DeleteFolder(string strPath)
{
    //删除这个目录下的所有子目录
    if (Directory.GetDirectories(strPath).Length > 0)
    {
        foreach (string fl in Directory.GetDirectories(strPath))
        {
            Directory.Delete(fl, true);
        }
    }
    //删除这个目录下的所有文件
    if (Directory.GetFiles(strPath).Length > 0)
    {
        foreach (string f in Directory.GetFiles(strPath))
        {
            System.IO.File.Delete(f);
        }
    }
    Directory.Delete(strPath, true);
}