PhotoSearchOptions options = new PhotoSearchOptions();

string userId = FUserIdInput[i];
if(!string.IsNullOrEmpty(userId)) options.UserId = userId;

if(!string.IsNullOrEmpty(FTagsInput[i]))
{
    options.Tags = FTagsInput[i];
}

options.PerPage = FPerPageInput[i];
options.TagMode = FTagModeInput[i];

FPhotoSearchOptions.Add(options);

private void DoSearch(int index)
{
    FConnectionInput[0].PhotosSearchAsync(FPhotoSearchOptionsInput[index], AssignResult);
}

private void AssignResult(FlickrResult<PhotoCollection> searchResult)
{
    FPhotoCollections.Add(searchResult.Result);
}