Below is the code I'm using.

UpdateMultipulGroupContactId = "1,2,3,4";

Client Side function

function UpdateMultipulGroup() {
    jQuery.ajax({
        url: "/Json/Contact_Update_Groups_NickName",
        type: "POST",
        data: {
            rid: UpdateMultipulGroupContactId,
            gids: strArray,
            nickname: 'abc'
        },
        dataType: "html",
        success: function (data) {
            var data = JSON.parse(data);
            alert(data.message);
            $("#Notes" + EditContactIdNotes).html($("#txtNotes").val());
            CloseLightBox();
        },
        error: function (error) {
            alert(error);
        }
    });

}

Server Side Function

public ActionResult Contact_Update_Groups_NickName(long rid, List<long> gids, string nickname)

I tried using arrays but I'm getting null values all the time.

How can I pass the UpdateMultipulGroupContactId as a list from this function?

Binding to IList<T>

This blog post of mine can help substantionally because it basically talks about this very problem. How to bind client data to an IList<T> in the controller action.

Blog post explains that values actually have to indexed as in

gids[0] = 1;
gids[1] = 2;

Sending complex JSON objects

But I've also written a very simple jQuery plugin that does all the conversion from a complex JSON object to an object that will easily be consumed by the MVC model binder. It is also able to consume various data types (dates etc) and convert them correctly for the Asp.net MVC to work out of the box without any changes on the server side.

By complex objects I mean JSON object with more than one level of hierarchy depth. Because the more complex the JSON object the more manipulation you have to do in your code. Plugin simplifies that to a single function call and providing it your JSON object.

Using the plugin would change your code to:

var data = {
    rid: 1234567890, // this is a "long" number
    gids: [1,2,3,4], // or "1,2,3,4".split(",")
    nickname: 'abc'
};

function UpdateMultipulGroup() {
    jQuery.ajax({
        url: "/Json/Contact_Update_Groups_NickName",
        type: "POST",
        data: $.toDictionary(data),
        success: ...
        ...
     });
}