gistfile1.cs

if (user.IsGoldPartner()) 
{
 // do something
}

public class User
{
       public int PostedPostCount { get; set; }
       public DateTime LastActivityDate { get; set; }
       public bool IsGoldPartner()
       {
           return this.PostedPostCount > 100 && this.LastActivityDate >= DateTime.Today.AddMonths(-3)
       }
}