public void Insert(int index, FileFilterItem ff)
 {
     if (_disposed)
     {
         throw new ObjectDisposedException("DialogFileFilterBuilder");
     }
     this.innerList.Insert(index, ff);
 }
 public void Append(FileFilterItem ff)
 {
     if (_disposed)
     {
         throw new ObjectDisposedException("DialogFileFilterBuilder");
     }
     this.innerList.Add(ff);
 }