Чтобы передавать куки от запроса к запросу нужно создать Cookies и передавать его при каждом вызове
Примеры использования:
Uri url = new Uri("http://example.com/api/method");
KeyValuePair<string, string>[] headers = new KeyValuePair<string, string>[]
{
new KeyValuePair<string, string>("Accept", "text/plain"),
new KeyValuePair<string, string>("Accept-Encoding", "br")
};
Dictionary<string, string> p = new Dictionary<string, string>
{
{ "query", "xxx" },
{ "filter", "birth" },
{ "count", "10" },
{ "offset", "0" }
};
WebCallResult resp = await WebCall.PostCallAsync(url, null, p, headers);
string responseString = await resp.GetResponseAsync();
var content = new StringContent("{"name":"John","age":30,"cars":[ "Ford", "BMW", "Fiat" ]}", Encoding.UTF8, "application/json");
resp = await WebCall.PostCallAsync(url, null, content, headers);
responseString = await resp.GetResponseAsync();