C# - How To Call A Javascript Method From Code - Behind Web Method

I have a web method in my code behind:

[System.Web.Services.WebMethod]
public static string GetStateData(string state)
{
//this is where i want to call a javascript method "GetItems"
}

I have a javascript method that retrieves some values for me and I want to get use one of those values in my web method

function GetItems() {
var variable1= $("#<%=Item1.ClientID %> input:checked");
var variable2= $("#<%=Item2.ClientID %>").val();
return [variable1.text(), variable2.val(), variable2];}


I've searched for ways to call the javascript method from the web method but every time my search results in how to call a web method from javascript.

I did find this but it was done from the code-behind of a silverlight project and when I tried adding the correct reference to my code-behind it wasn't there

var result = HtmlPage.Window.Invoke("GetItems"); Is there a reference I'm missing?