尝试包括你的查询字符串即basestring：

  VAR baseFormat =oauth_consumer_key = {0}＆安培; oauth_nonce = {1}＆安培; oauth_signature_method = {2}+
                  ＆放大器; oauth_timestamp = {3}＆安培;组oauth_token = {4}＆安培; oauth_version = {5}＆安培;轨道= {6};
无功即basestring =的String.Format（baseFormat，
                                    oauth_consumer_key，
                                    oauth_nonce，
                                    oauth_signature_method，
                                    oauth_timestamp，
                                    组oauth_token，
                                    oauth_version，
                                    Uri.EscapeDataString（valueToTrack）
                                    ）;
 

...

  VAR postBody =轨道=奥巴马;
 

https://dev.twitter.com/docs/auth/creating-signature 说：
5.带百分比code参数字符串，并将其追加到输出字符串。

I got some code for Twitter update and search api from CodeProject which worked just fine.

However, i get 401 when i tried to convert it for the stream api: "https://stream.twitter.com/1/statuses/filter.json". I will appreciate any help. See code below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Security.Cryptography;
using System.IO;

public class OAuthRead
{
    public static void Authenticate()
    {
        // oauth application keys
        var oauth_consumer_key = "****";
        var oauth_consumer_secret = "*****";
        var oauth_token = "******";
        var oauth_token_secret = "******";

        // oauth implementation details
        var oauth_version = "1.0";
        var oauth_signature_method = "HMAC-SHA1";

        // unique request details
        var oauth_nonce = Convert.ToBase64String(
        new ASCIIEncoding().GetBytes(DateTime.Now.Ticks.ToString()));
        var timeSpan = DateTime.UtcNow
        - new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
        var oauth_timestamp = Convert.ToInt64(timeSpan.TotalSeconds).ToString();

        //var resource_url = "https://stream.twitter.com/1/statuses/filter.json?track=obama&include_entities=1&language=en";
        //var resource_url = "https://api.twitter.com/1.1/statuses/user_timeline.json";
        var resource_url = "https://stream.twitter.com/1.1/statuses/filter.json";
        //var screen_name = "femitfash";
        // create oauth signature
        var baseFormat = "oauth_consumer_key={0}&oauth_nonce={1}&oauth_signature_method={2}" +
        "&oauth_timestamp={3}&oauth_token={4}&oauth_version={5}";

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

        baseString = string.Concat("POST&", 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)));
        }

        // create the request header
        var headerFormat = "OAuth oauth_nonce=\"{0}\", oauth_signature_method=\"{1}\", " +
        "oauth_timestamp=\"{2}\", oauth_consumer_key=\"{3}\", " +
        "oauth_token=\"{4}\", oauth_signature=\"{5}\", " +
        "oauth_version=\"{6}\"";

        var authHeader = string.Format(headerFormat,
        Uri.EscapeDataString(oauth_nonce),
        Uri.EscapeDataString(oauth_signature_method),
        Uri.EscapeDataString(oauth_timestamp),
        Uri.EscapeDataString(oauth_consumer_key),
        Uri.EscapeDataString(oauth_token),
        Uri.EscapeDataString(oauth_signature),
        Uri.EscapeDataString(oauth_version)
        );


        // make the request

        ServicePointManager.Expect100Continue = false;

        var postBody = "track=obama&include_entities=1&language=en"; // "screen_name=" + Uri.EscapeDataString(screen_name);//
        resource_url += "?" + postBody;
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(resource_url);
        request.Headers.Add("Authorization", authHeader);
        request.Method = "POST";
        request.ContentType = "application/x-www-form-urlencoded";
        request.PreAuthenticate = true;
        request.AllowWriteStreamBuffering = true;

        WebResponse response = request.GetResponse();
        string responseData = new StreamReader(response.GetResponseStream()).ReadToEnd();

    }
}

try include your query string to baseString:

var baseFormat = "oauth_consumer_key={0}&oauth_nonce={1}&oauth_signature_method={2}" +
                  "&oauth_timestamp={3}&oauth_token={4}&oauth_version={5}&track={6}";
var baseString = string.Format(baseFormat,
                                    oauth_consumer_key,
                                    oauth_nonce,
                                    oauth_signature_method,
                                    oauth_timestamp,
                                    oauth_token,
                                    oauth_version,
                                    Uri.EscapeDataString(valueToTrack)
                                    );

....

var postBody = "track=obama";

https://dev.twitter.com/docs/auth/creating-signature says: 5. Percent encode the parameter string and append it to the output string.