public enum RegistrationType : System.Enum, System.IComparable, System.IConvertible, System.IFormattable  

public bool IsTableVersioned(Geodatabase geodatabase, string tableName)
{
  using (Table table = geodatabase.OpenDataset<Table>(tableName))
  {
    // Check table version type
    RegistrationType registrationType = table.GetRegistrationType();
    if (registrationType == RegistrationType.Versioned)
    {
      return true;
    }
  }
  return false;
}