ASP.NET Ajax jquery input parameter is null

Question

I have a problem with this.
below are my jquery code and aspx.cs code.
I should send $('#UserID').val() to WebMethod as a parameter.
but in WebMethod it is always null.
if I change $('#UserID').val() to any string, it works well.
#UserID is correct. because I made a alert window with this value.
and.. I already changed data: '{userId: "' + $('#UserID').val() + '"}',
to data: JSON.stringify({ userId: $('#UserID').val() }).
but nothing works.

 $.ajax({
    url: "register.aspx/IsIdAvailable",
    type: "post",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    data: '{userId: "' + $('#UserID').val() + '"}',
    dataFilter: function (data) {
        var msg = JSON.parse(data);
        if (msg.hasOwnProperty('d'))
            return msg.d;
        else
            return msg;
    }
})

[WebMethod]
public static bool test(string userId)
{
    System.Diagnostics.Trace.WriteLine("userId: " + userId +"!");
    ...
}

output is always userId: !

apparently $('#UserID').val() is null. Can you try this: alert($('#UserID').val()); ? — renakre
– renakre, Commented Apr 15, 2015 at 18:12
Watch the network request in your browser debug console to see how it is posted to your server-side code. — Jasen
– Jasen, Commented Apr 15, 2015 at 18:12
You don't need the single quote. Change it to: data: {userId : $('#UserID').val() }, — lloyd christmas
– lloyd christmas, Commented Apr 15, 2015 at 18:15
I did everything you guys said. but it doesn't work. but thank you all. — user4793203
– user4793203, Commented Apr 15, 2015 at 18:38
You wrote register.aspx/IsIdAvailable in the script but test in C#. Is it a mistake in copy paste here? — Vitor Canova
– Vitor Canova, Commented Apr 15, 2015 at 18:59

Mark · Accepted Answer · 2015-04-15 18:08:09Z

1

Try changing your data attribute to something like:

data: {'userId': $("#UserID").val()}

answered Apr 15, 2015 at 18:08

Mark

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