CODEWITHSUNDEEP
c#xmlhttprequest
Elfayer
Elfayer

Reputation: 23

How do I use AJAX to upload files to ASP.NET?

I am trying to upload files using AJAX to ASP.NET. I have this Javascript:

var xhr = new XMLHttpRequest();

for (var i = 0; i < files.length; i++) {
   xhr.open('post', '/File/Upload', true);
   xhr.setRequestHeader("Content-Type", "multipart/form-data");
   var formData = new FormData();
   formData.append("_file", files[i]);
   xhr.send(files[i]);
}

files is an Array()

Then I try to access the post file in C# code, but the value is always null. How can I resolve this issue?

// Method 1, Result: file = null
HttpPostedFileBase file = Request.Files["_file"];

// Method 2, Result: postedFile.Count = 0
HttpFileCollectionBase postedFile = Request.Files;

Upvotes: 2

Views: 16310

Answers (2)

VRC
VRC

Reputation: 761

You can also use jQuery

you have 2 functions
Ajax : http://api.jquery.com/jQuery.ajax/
Load(shortcut, calls ajax) : http://api.jquery.com/load/
Examples : http://www.w3schools.com/jquery/jquery_ajax.asp

Edited : 2012-10-04 16:31
Reason : Got the following Comment :
Hm unless I don't understand, I don't want to load informations of the server, I want to get the informations I have in my JS code on my server. I already have the informations to send in the files Array(). – Elfayer

What you do is you make a AJAX call to the server like to an webservice. Here is an example

var value = 1;
var handlerUrl = [YOUR WEBSERVICE URL];

//Do the Ajax Call
jQuery.ajax({
  url: handlerUrl,
  data: { "params[]": [value] },
  type: 'POST',
  success: function (data)
  {
     alert("succes");
  },
  error: function (jxhr, msg, err)
  {
     alert("error");
  }
});

in the data parameter you give your data.
I send it here in the form of an array but you can send it also like 1 parameter. How do you access it in well in my case a generic handler.

//Split the parameters and set in Array of Strings
var param = context.Request.Form[0].Split(',');
var value = param[0];

Like I said I give it in the form of an array so I only have one parameter
and then I split it. But if you would give it like single properties then you
could get it like : 

context.Request.Form[0]
context.Request.Form[1]
context.Request.Form[2]
context.Request.Form[3]
context.Request.Form[4]

Upvotes: 0

Darin Dimitrov
Darin Dimitrov

Reputation: 1039508

Assuming you have the following form containing the file input field:

<form action="/home/index" method="post" enctype="multipart/form-data" onsubmit="return handleSubmit(this);">
    <input type="file" id="_file" name="_file" multiple="multiple" />
    <button type="submit">OK</button>
</form>

you could try the following function:

function handleSubmit(form) {
    if (!FormData) {
        alert('Sorry, your browser doesn\'t support the File API => falling back to normal form submit');
        return true;
    }

    var fd = new FormData();
    var file = document.getElementById('_file');
    for (var i = 0; i < file.files.length; i++) {
        fd.append('_file', file.files[i]);
    }

    var xhr = new XMLHttpRequest();
    xhr.open(form.method, form.action, true);
    xhr.onreadystatechange = function () {
        if (xhr.readyState == 4 && xhr.status == 200) {
            alert(xhr.responseText);
        }
    };
    xhr.send(fd);

    return false;
}

Now on the server you should be able to retrieve the file using Request.Files.

Upvotes: 3

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