Not able to set tweets count and exclude retweets from the fetched results?

[aveeral]

I am trying to use twitter API 1.1 to fetch user timeline. I am able to fetch latest tweets but it is limited to 20.
How to set the count and exclude retweets from it? I am trying something like this

var baseFormat = "oauth_consumer_key={0}&oauth_nonce={1}&oauth_signature_method={2}" +
                            "&oauth_timestamp={3}&oauth_token={4}&oauth_version={5}&screen_name={6}&count={7}&exclude_replies={8}";

            var baseString = string.Format(baseFormat,
                                        oauth_consumer_key,
                                        oauth_nonce,
                                        oauth_signature_method,
                                        oauth_timestamp,
                                        oauth_token,
                                        oauth_version,
                                         Uri.EscapeDataString(screen_name),
                                         Uri.EscapeDataString(count),
                                         Uri.EscapeDataString(exclude_replies)
                                        );

            baseString = string.Concat("GET&", Uri.EscapeDataString(resource_url), "&", Uri.EscapeDataString(baseString));

            var compositeKey = string.Concat(Uri.EscapeDataString(oauth_consumer_secret),
                                    "&", Uri.EscapeDataString(oauth_token_secret));

            string oauth_signature;
            using (HMACSHA1 hasher = new HMACSHA1(ASCIIEncoding.ASCII.GetBytes(compositeKey)))
            {
                oauth_signature = Convert.ToBase64String(
                    hasher.ComputeHash(ASCIIEncoding.ASCII.GetBytes(baseString)));
            }