HTTPI unable to pass array params

Question

@request.url     = url
@request.headers = {"Content-Type" => "application/x-www-form-urlencoded; charset=utf-8"}
@request.body    = {a: "1", b: "2", c: [{d: "3"}, {e: "4"}]}

The problem is that the server side could receive params like a or b, but each value of c is null, like "c": [{"d": null}, {"e": null}]. Any help will be appreciated.

[Solved] :) The server use .net and I don't know what they did..