ASP.NET Ajax, by default, makes HTTP POST for all web service calls. HTTP POST is more expensive than HTTP GET. It transmits more bytes over the wire, thus taking precious network time, and it also makes ASP.NET do extra processing on the server end. So, you should use HTTP GET as much as possible. However, HTTP GET does not allow you to pass objects as parameters. You can pass numerics, strings and dates only. When you make an HTTP GET call, Atlas builds an encoded URL and makes a hit to that URL. So, you must not pass too much content that makes the URL become larger than 2048 characters. As far as I know, that's the max length of any URL. In order to enable HTTP GET on a web service method, you need to decorate the method with the [ScriptMethod(UseHttpGet=true)] attribute:
[WebMethod] [ScriptMethod(UseHttpGet=true)]
public string HelloWorld()
{
}
