request.files中没有文件

Question

I have web project with entity framework 6.0 I upload file with Javascript in xmlhttprequest but in server side when I want catch the file with request.files request.files is empty! I upload file with dropzone,but after a time without result i try js code like below but the probleam is same to dropzone.js

What I have tried:

javascript code:

var that = this;
debugger;
var url = "../../Ajax/GlobalHandler.aspx?Command=UploadImage";
var xhr = new XMLHttpRequest();
var fd = new FormData();
xhr.open("POST", url, true);
xhr.onreadystatechange = function () {
    if (xhr.readyState == 4 && xhr.status == 200) {
    // Every thing ok, file uploaded
        console.log(xhr.responseText); // handle response.
    }
};
fd.append("upload_file", file);
xhr.setRequestHeader("Content-Type", "multipart/form-data");
//xhr.setRequestHeader("Content-Type", "application/json");
xhr.setRequestHeader("X-File-Name", file.name);
xhr.setRequestHeader("X-File-Size", file.size);
xhr.setRequestHeader("X-File-Type", file.type); 
xhr.send(fd);

c# code:

Guid fileGuid = Guid.NewGuid();
string fileName = string.Empty;

foreach (string s in Request.Files)
{
    HttpPostedFile File = Request.Files[s];

    if (File == null || string.IsNullOrEmpty(File.FileName))
        continue;

    var fileContent = new byte[File.InputStream.Length];

    File.InputStream.Read(fileContent, 0, fileContent.Length);
    File.InputStream.Close();
    File.InputStream.Dispose();

    var dot = File.FileName.LastIndexOf(".");
    var ext = string.Empty;
    if (dot >= 0)
        ext = File.FileName.Substring(dot + 1);

    fileName = fileGuid.ToString() + (string.IsNullOrEmpty(ext) ? string.Empty : "." + ext);
    FileStream filestream = new FileStream(Context.Server.MapPath("~/App_Data") + "\\" + fileName, FileMode.Create);
    filestream.Write(fileContent, 0, fileContent.Length);
    filestream.Close();
    filestream.Dispose();
}