Question

I’m building an MVC application which uses Windows Authentication. I want to handle a dropdownlist change event by making a post to the server with Jquery post.

Below is the Controller method I want to invoke:

[HttpPost]
public JsonResult UpdateConversion(int conversionId, int? conversionStandardId)
{
    // Some statements here
}

And below is the javascript function that handles the onchange event of the dropdown:

function onConversionValueChange() {
    var input = $(this);
    var conversionId = input.attr('id').replace('ConversionFor', '');
    var selectedValue = input.val();

    if (selectedValue == '') {
        $.post(Conversions._UpdateConversionURL, { conversionId: conversionId }, onConversionValueChanged);
    }
    else {
        $.post(Conversions._UpdateConversionURL, { conversionId: conversionId, conversionStandardId: selectedValue }, onConversionValueChanged);
    }
}

I don’t think there’s something wrong with these methods, because when I load the page initially and do the change the post call works several times. But after a while, it calls the post 3 times in a single event and returns 401 unauthorized error on all of them. Although the third call seemed to be successful.

Anyone can help me with this? Thanks.

Answer 1

That’s exactly how Windows Authentication (NTLM) works. It’s a challenge/response authentication scheme where the client sends a request, the server challenges the client to prove that he has the correct credentials by generating a nonce, and then the client authenticates. You can read more here: http://www.innovation.ch/personal/ronald/ntlm.html

Normally once authenticated the user agent should not need to go through all the phases on subsequent requests and should directly be able to send the authentication credentials.