How to automatically logout from the twitter account using oauth in c# web application?

protected void Page_Load ( object sender, EventArgs e )
{
    if ( Request.QueryString[ "oauth_token" ] != null && Request.QueryString[ "oauth_verifier" ] != null )
    {
        string oauth_token = Request.QueryString[ "oauth_token" ];
        string oauth_verifier = Request.QueryString[ "oauth_verifier" ];

        OAuthHelper oauthhelper = new OAuthHelper ( );
        oauthhelper.GetUserTwAccessToken ( oauth_token, oauth_verifier );

        if ( string.IsNullOrEmpty ( oauthhelper.oauth_error ) )
        {
            Session[ "twtoken" ] = oauthhelper.oauth_access_token;
            Session[ "twsecret" ] = oauthhelper.oauth_access_token_secret;
            Session[ "twuserid" ] = oauthhelper.user_id;
            Session[ "twname" ] = oauthhelper.screen_name;


            Response.Write ( "AccessToken=" + oauthhelper.oauth_access_token );
            Response.Write ( "<br />Access Secret=" + oauthhelper.oauth_access_token_secret );
            Response.Write ( "<br />Screen Name=" + oauthhelper.screen_name );
            Response.Write ( "<br />Twitter User ID=" + oauthhelper.user_id );

            OAuthTokens tokens = new OAuthTokens ( );
            tokens.ConsumerKey = "ConsumerKey";
            tokens.ConsumerSecret = "ConsumerSecret";
            tokens.AccessToken = oauthhelper.oauth_access_token;
            tokens.AccessTokenSecret = oauthhelper.oauth_access_token_secret;

            var objuserdata = TwitterUser.Show ( tokens, oauthhelper.screen_name );

            ImageConverter objImageConverter = new ImageConverter ( );
            System.Drawing.Image myImage = System.Drawing.Image.FromFile ( Server.MapPath ( "~/1250x570.jpg" ) );

            byte[ ] photo = File.ReadAllBytes ( Server.MapPath ( "~/1250x570.jpg" ) );
            TwitterResponse<twitterstatus> response = TwitterStatus.UpdateWithMedia ( tokens, "img", photo );
            if ( response.Result == RequestResult.Success )
            {
                Response.Write ( "This is YOUR PAGE" );
            }
            else
            {
                Response.Write ( "Try some other time" );
            }

        }
        else
            Response.Write ( oauthhelper.oauth_error );
    }
    else
    {
        //Display some information about the user
        ShowUserInfo ( );
    }

}

private void ShowUserInfo ( )
{
    OAuthHelper oauthhelper = new OAuthHelper ( );
    string requestToken = oauthhelper.GetRequestToken ( );

    if ( string.IsNullOrEmpty ( oauthhelper.oauth_error ) )
        Response.Redirect ( oauthhelper.GetAuthorizeUrl ( requestToken ) );
    else
        Response.Write ( oauthhelper.oauth_error );

}