Web API Form Data Collection

I’m trying to post form serialized values to controller (Web API Self Host).
I cannot understand why the NameValueCollection is not correctly bound.
Client-side using jQuery:

// Form Submit Handler
$( '#form-parameters' ).submit(function (event) {


        var formData = $(this).serialize();
        // Post serialized form data

// Post Form Data to controller test
function postAssemblyParameters(formData){
                url: http://localhost/api/test/1,
                type: 'POST',
                data: formData,
                dataType: 'application/x-www-form-urlencoded',
                success: function(x3d) {
                error: function(xhr) {


Server-side using Web API Self Host:
public void Post([FromUri] int id, [FromBody] NameValueCollection formData)
        Console.WriteLine(id); // OK

        // Collection is NULL
        foreach (var key in formData.AllKeys)
                foreach (var val in formData.GetValues(key))
                        Console.WriteLine(key + ": " + val);

Many thanks.


Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

Instead of NameValueCollection, try FormDataCollection.


Method 2

Or you can use the build “ReadAsNameValueCollection”, like this :

NameValueCollection MyNameValueCollection = formData.ReadAsNameValueCollection();

Method 3

Thanks Scott. Your answer was just what I needed. Based on it, I wrote the following little utility method that will come in handy as it pulls all the data values out of the stream (using the FormDataCollection) and puts them into a NamedValueCollection (which you can access in any order you want).

/// <summary>
/// Copy the values contained in the given FormDataCollection into 
/// a NameValueCollection instance.
/// </summary>
/// <param name="formDataCollection">The FormDataCollection instance. (required, but can be empty)</param>
/// <returns>The NameValueCollection. Never returned null, but may be empty.</returns>
public static NameValueCollection Convert(FormDataCollection formDataCollection)
    Validate.IsNotNull("formDataCollection", formDataCollection);

    IEnumerator<KeyValuePair<string, string>> pairs = formDataCollection.GetEnumerator();

    NameValueCollection collection = new NameValueCollection();

    while (pairs.MoveNext())
        KeyValuePair<string, string> pair = pairs.Current;

        collection.Add(pair.Key, pair.Value);

    return collection

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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