title: X509SecurityToken is missing under Namespace of System.IdentityModel.Tokens
body: <p>I have installed Nuget package of "JSON Web Token Handler For the Microsoft .Net Framework 4.5" (link:- <a href="http://www.nuget.org/packages/System.IdentityModel.Tokens.Jwt/" rel="nofollow">http://www.nuget.org/packages/System.IdentityModel.Tokens.Jwt/</a>) for visual studio 2012. But it doesn't contains a definition for "X509SecurityToken". Which cause to show errors in following method...</p>
  
  <pre><code>   private static void ValidateToken(string Token)
     {
          var tokenHandler = new JwtSecurityTokenHandler();
          var validationParameters = new TokenValidationParameters()
          {
              ValidAudience = "&lt;some url&gt;",
              IssuerSigningTokens = new List&lt;X509SecurityToken&gt;() { new X509SecurityToken(
             X509
             .LocalMachine
             .My
             .Thumbprint
             .Find("112233445566xxyy", false)
             .First()) },
              ValidIssuer = "https://my-issuer.com/trust/issuer",
              CertificateValidator = X509CertificateValidator.None,
              RequireExpirationTime = true
          };
  
          try
          {
              SecurityToken validatedToken;
              var principal = tokenHandler.ValidateToken(Token, validationParameters, out validatedToken);
          }
          catch (Exception e)
          {
  
              Console.WriteLine("{0}\n {1}", e.Message, e.StackTrace);
          }
  
          Console.WriteLine();
      }
  </code></pre>
  
  <p>If anyone can provide any help or even hints I would greatly appreciated, </p>
  
  <p>Thanks for helping,
  Kushan Randima.</p>