Add Newtonsoft.Json.dll file as resource

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in "web config" in appsettings add keys


 
  <add key="ClientID" value="xxxxx" />
  <add key="ClientSecret" value="xxxxxxx" />
  <add key="WebServiceURL" value="xxxxxxxxx" />


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// put this class on same login page

public class UserInfo
{
    public bool IsValid { get; set; }
    public string Token { get; set; }
    public string NationalID { get; set; }
    public string DisplayName { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Sid { get; set; }
    public string Email { get; set; }
    public int? UserTypeID { get; set; }
    public string Mobile { get; set; }
}


public class AjaxWrapper<T>
{
    public T d;
}





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// In Login Page In load Function 


 
    if (!(Request.QueryString("Token") == null))
    {
        string Token = Request.QueryString("Token").ToString();
        string ClientID = WebConfigurationManager.AppSettings("ClientID").ToString();
        string ClientSecret = WebConfigurationManager.AppSettings("ClientSecret").ToString();
        string WebServiceURL = WebConfigurationManager.AppSettings("WebServiceURL").ToString();
        string SrtWebServiceURL = string.Format(WebServiceURL + "/GetUserInfoFromApp?Token='{0}'&ClientID='{1}'&ClientSecret='{2}'", HttpUtility.UrlEncode(Token), HttpUtility.UrlEncode(ClientID), HttpUtility.UrlEncode(ClientSecret));
        WebClient wc = new WebClient();
        string data = wc.DownloadString(SrtWebServiceURL);
        UserInfo result = Newtonsoft.Json.JsonConvert.DeserializeObject<AjaxWrapper<UserInfo>>(data).d;

 If (result !=null && result.IsValid ){

               // Token is valid 
              // here  you got the  NationalID  of user  result.NationalID
             // your turn now to enter user to your system   
               } 
           else{
             // You know from here "Invalid token or entry"
            // let user show your login page cause he is not authorized as SSO
           }


    }



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