Fetch Zotero collection items recursively with pagination (C#)

using System.Linq;

string url = "https://api.zotero.org/users/<userID>/collections/GDRUMMLB/items/top";
string responseText = string.Empty;
while (true) {
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
    request.Method = "GET";
    request.Headers.Add("Zotero-API-Version", "3");
    request.Headers.Add("Zotero-API-Key", "<apiKey>");

    using (WebResponse resp = request.GetResponse())
    {
        var links = new Dictionary<string, string>();
        var linkHeader = resp.Headers.GetValues("Link");
        var matches = Regex.Matches(linkHeader[0], @"<(?<url>[^>]*)>;\s+rel=""(?<link>\w+)\""");
        foreach (Match m in matches)
            links.Add(m.Groups["link"].Value, m.Groups["url"].Value);
        //links.Select(i => $"{i.Key}: {i.Value}").ToList().ForEach(Console.WriteLine);

        Stream respStream = resp.GetResponseStream();
        using (StreamReader sr = new StreamReader(respStream))
        {
            responseText += sr.ReadToEnd();
        }
        if (!links.ContainsKey("next"))
        {
            break;
        }
        else
        {
            url=links["next"];
            System.Threading.Thread.Sleep(1000);
        }
    }
}
Console.WriteLine(responseText);
File.WriteAllText("c:\\temp\\output.json", responseText.Replace("][",","));