上传的文件如果不在本地主机上，会以blob的形式出现吗?asp.net mvc4使用IIS express

我的网站在本地网络上运行，允许用户上传zip文件。但是当我开始在局域网（而不是本地主机）上测试它时，文件显示为blob？例如：在运行IIS express的本地主机上，我可以上传example.zip，它在上传文件夹中显示为example.zip。现在，如果我尝试从另一台机器上传，example.zip显示为blob。有趣的是，如果我将文件重命名回example.zip，并给出正确的扩展名，文件就完全完整，我可以读取它。我认为这可能是文件夹权限，所以我让每个人都完全控制上传文件夹进行测试，但它仍然不起作用。这是我的API控制器的代码，它保存了进来的文件

public class UploadController : ApiController
{
    // Enable both Get and Post so that our jquery call can send data, and get a status
    [HttpGet]
    [HttpPost]
    public HttpResponseMessage Upload()
    {
        // Get a reference to the file that our jQuery sent.  Even with multiple files, they will all be their own request and be the 0 index
        HttpPostedFile file = HttpContext.Current.Request.Files[0];
        // do something with the file in this space
        if (File.Exists(HttpContext.Current.Server.MapPath("~/App_Data/uploads/test/" + file.FileName)))
        {
            Stream input = file.InputStream;
            FileStream output = new FileStream(HttpContext.Current.Server.MapPath("~/App_Data/uploads/test/" + file.FileName), FileMode.Append);
            byte[] buffer = new byte[8 * 1024];
            int len;
            while ((len = input.Read(buffer, 0, buffer.Length)) > 0)
            {
                output.Write(buffer, 0, len);
            }
            input.Close();
            output.Close();
        }
        else
        {
            file.SaveAs(HttpContext.Current.Server.MapPath("~/App_Data/uploads/test/" + file.FileName));
        }
        // end of file doing

        // Now we need to wire up a response so that the calling script understands what happened
        HttpContext.Current.Response.ContentType = "text/plain";
        var serializer = new System.Web.Script.Serialization.JavaScriptSerializer();
        var result = new { name = file.FileName};
        HttpContext.Current.Response.Write(serializer.Serialize(result));
        HttpContext.Current.Response.StatusCode = 200;
        // For compatibility with IE's "done" event we need to return a result as well as setting the context.response
        return new HttpResponseMessage(HttpStatusCode.OK);
    }
}

你知道为什么我的文件被保存为blob吗？谢谢

var filenameHeader = HttpContext.Current.Request.Headers.Get("Content-Disposition");