NOT Able to connect to LDAP Server

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C#

ASP.NET

LDAP

PrincipalContext ctx = new PrincipalContext(ContextType.ApplicationDirectory, "domain.com", "ou=*Garden City Users, o=microsoft,c=us", ContextOptions.SecureSocketLayer | ContextOptions.SimpleBind, "CN=ppatel, OU=*Garden City Users, O=Microsoft, C=US ", "password");
           UserPrincipal up = UserPrincipal.FindByIdentity(ctx, IdentityType.Name,"ppatel");

           if (up != null)
           {
               PrincipalSearchResult<Principal> Results = up.GetAuthorizationGroups();
               foreach (Principal Result in Results)
               {
                   Response.Write(Result.Name);
               }
           }

I am trying to get all the group to which user is associated. My code is above. when i am trying to run it i am getting error that LDAP SERVER IS UNAVAILABLE ....

Can anyone please help on this

Thanks
PPatel