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Posted 29 Aug 2011


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Twitter OAuth authentication using .NET

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26 Aug 2014CPOL3 min read
A example showing how to authenticate a Twitter application using oAuth and the application access token.


In this article, I want to demonstrate how to implement OAuth authentication in .NET. I've previously written about my dislike of third party SDKs for social media integration and how we should leverage technology based solutions instead. One of the sticking points in doing this tends to be that implementing OAuth based authentication is relatively difficult compared with actually making the requests themselves. There is documentation available, but there seems to be a lack of .NET example code to go with it.

In keeping with my thoughts in previous articles, I would recommend using open source OAuth based libraries to solve this problem, and again avoid resorting to third party Twitter/Facebook implementations which more strongly couple code to specific APIs. This keeps the solution more reusable and builds on specific technologies to better future proof your application.

I've also previously shown how client-side plug-ins can be used in combination with server-side code to speed development in this area. However, sometimes authentication does need to be implemented purely on the server-side.

So how difficult is this?

It turns out implementing OAuth on the server-side in .NET isn't too difficult, the battle is getting the encoding and authentication signature right. With so few examples, it can be a little daunting, so here's an example written in pure .NET using the official Twitter OAuth documentation and a bit of trial and error.


The following example shows how to authenticate against the Twitter APIs using a registered Twitter application. Any interaction with the APIs when authenticated in this manner will behave as if coming from the Twitter account under which the application has been registered. It's therefore useful for sending out status updates or sending out notifications from a specific account.

Usually OAuth requires redirecting the user to a login screen to obtain an oAuth token which requires a bit more work. However, when authenticating via a Twitter application, this step is skipped as your application already has an oAuth token provided (access token). Whether you are using the application oAuth token or a user oAuth token, the following code can be used to authenticate against the Twitter APIs.

The Code

The first step is to visit the Twitter developer section and register a new application. On completion, you will be provided with a set of public/private keys which you will need the replace in the example below in order to run. The values I have used directly correspond with the documented example here. Make sure you replace them with your own.

var oauth_token           = "819797-Jxq8aYUDRmykzVKrgoLhXSq67TEa5ruc4GJC2rWimw";
var oauth_token_secret    = "J6zix3FfA9LofH0awS24M3HcBYXO5nI1iYe8EfBA";
var oauth_consumer_key    = "GDdmIQH6jhtmLUypg82g";
var oauth_consumer_secret = "MCD8BKwGdgPHvAuvgvz4EQpqDAtx89grbuNMRd7Eh98";

We also need to define some details about the request. This includes a unique oauth_nonce parameter which must be generated per request, and a timestamp.

var oauth_version          = "1.0";
var oauth_signature_method = "HMAC-SHA1";
var oauth_nonce            = Convert.ToBase64String(
                                  new ASCIIEncoding().GetBytes(
var timeSpan               = DateTime.UtcNow
                                  - new DateTime(1970, 1, 1, 0, 0, 0, 0,
var oauth_timestamp        = Convert.ToInt64(timeSpan.TotalSeconds).ToString();
var resource_url           = "";
var status                 = "Updating status via REST API if this works";

The next step is to generate an encrypted oAuth signature which Twitter will use to validate the request. To do this, all of the request data is concatenated into a particular format as follows.

var baseFormat = "oauth_consumer_key={0}&oauth_nonce={1}&oauth_signature_method={2}" +

var baseString = string.Format(baseFormat,

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

Using this base string, we then encrypt the data using a composite of the secret keys and the HMAC-SHA1 algorithm.

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(

The oAuth signature is then used to generate the Authentication header. This requires concatenating the public keys and the token generated above into the following format.

var headerFormat = "OAuth oauth_nonce=\"{0}\", oauth_signature_method=\"{1}\", " +
                   "oauth_timestamp=\"{2}\", oauth_consumer_key=\"{3}\", " +
                   "oauth_token=\"{4}\", oauth_signature=\"{5}\", " +

var authHeader = string.Format(headerFormat,

We are now ready to send the request, which is the easy part. Note, we must also disable the Expect: 100-Continue header using the ServicePointManager. Without this code, .NET sends the header by default, which is not supported by Twitter.

var postBody = "status=" + Uri.EscapeDataString(status);

ServicePointManager.Expect100Continue = false;

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(resource_url);
request.Headers.Add("Authorization", authHeader);
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
using (Stream stream = request.GetRequestStream())
    byte[] content = ASCIIEncoding.ASCII.GetBytes(postBody);
    stream.Write(content, 0, content.Length);
WebResponse response = request.GetResponse();


This example hopefully shows how OAuth can be implemented with fairly little effort. In the example provided, I've kept everything inline for clarity; however, in the real world, you would obviously refactor the code into more sensible layers.

In this way, it's possible to build some highly testable lightweight classes in order to generate the required message signature, make the requests, and handle the response.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

United Kingdom United Kingdom
Mike Carlisle - Technical Architect with over 20 years experience in a wide range of technologies.


Comments and Discussions

QuestionOAuth Pin
Member 1304822221-Nov-17 0:14
MemberMember 1304822221-Nov-17 0:14 
QuestionI Am getting an error in authenticate a Twitter application using oAuth Pin
Member 1214236617-Nov-15 2:26
MemberMember 1214236617-Nov-15 2:26 
AnswerRe: I Am getting an error in authenticate a Twitter application using oAuth Pin
SGMoney17-Nov-15 10:05
MemberSGMoney17-Nov-15 10:05 
QuestionAdding Media Id Pin
Erika Liza Vergara12-Sep-15 5:50
MemberErika Liza Vergara12-Sep-15 5:50 
QuestionThank~ TheCodeKing Pin
Member 1039050520-May-15 4:31
MemberMember 1039050520-May-15 4:31 
Questiongetting error Pin
Member 1061473024-Mar-15 7:32
MemberMember 1061473024-Mar-15 7:32 
QuestionDoesnot work Pin
Member 140823826-Jan-15 20:05
MemberMember 140823826-Jan-15 20:05 
GeneralMy vote of 5 Pin
Thomas Maierhofer (Tom)26-Jan-15 6:09
MemberThomas Maierhofer (Tom)26-Jan-15 6:09 
QuestionCan not tweet more then 2 consecutive tweets in a row. Pin
Member 1128979818-Dec-14 6:05
MemberMember 1128979818-Dec-14 6:05 
QuestionRe: Can not tweet more then 2 consecutive tweets in a row. Pin
Member 1154959528-Mar-15 19:50
MemberMember 1154959528-Mar-15 19:50 
AnswerRe: Can not tweet more then 2 consecutive tweets in a row. Pin
Member 1154959529-Mar-15 2:56
MemberMember 1154959529-Mar-15 2:56 
AnswerRe: Can not tweet more then 2 consecutive tweets in a row. Pin
Member 1128979829-Mar-15 3:05
MemberMember 1128979829-Mar-15 3:05 
GeneralRe: Can not tweet more then 2 consecutive tweets in a row. Pin
Sung M Kim14-Aug-15 5:06
professionalSung M Kim14-Aug-15 5:06 
AnswerRe: Can not tweet more then 2 consecutive tweets in a row. Pin
Member 1080623124-May-17 2:19
MemberMember 1080623124-May-17 2:19 
QuestionError 401 Pin
William C. Rodrigues13-Nov-14 15:00
professionalWilliam C. Rodrigues13-Nov-14 15:00 
Questionheader format change Pin
Juanjo luvonovich25-Oct-14 3:57
MemberJuanjo luvonovich25-Oct-14 3:57 
QuestionError:The remote server returned an error: (403) Forbidden. Pin
FeroseKhan23-Sep-14 20:08
MemberFeroseKhan23-Sep-14 20:08 
AnswerRe: Error:The remote server returned an error: (403) Forbidden. Pin
Member 1006531319-Mar-15 16:43
MemberMember 1006531319-Mar-15 16:43 
Question401 hatası alıyorum. I am taking still 401 error. Pin
ercandemir3-Sep-14 1:45
professionalercandemir3-Sep-14 1:45 
QuestionTo Make it work just make two changes Pin
DarkNetMaster17-Apr-14 17:49
MemberDarkNetMaster17-Apr-14 17:49 
AnswerRe: To Make it work just make two changes Pin
Manuel M.N.25-Aug-14 22:09
MemberManuel M.N.25-Aug-14 22:09 
AnswerRe: To Make it work just make two changes Pin
Manuel M.N.25-Aug-14 22:12
MemberManuel M.N.25-Aug-14 22:12 
AnswerRe: To Make it work just make two changes Pin
gazal20128-Nov-14 5:30
Membergazal20128-Nov-14 5:30 
GeneralMy vote of 1 PinPopular
Georgettekh11-Apr-14 3:33
MemberGeorgettekh11-Apr-14 3:33 
QuestionThe remote server returned an error: (401) Unauthorized. Pin
Gun Gun Febrianza15-Nov-13 8:14
Member Gun Gun Febrianza15-Nov-13 8:14 

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