Razor skipping nested foreach loops - asp.net-mvc-3

Question

In my database I have a string of child tables. In a razor view I am trying to loop through the ultimate parent and then filter a collection a few levels down.
I have got it to work using the following extract:
#foreach (var artist in Model)
{
<tr>
<td>
#Html.DisplayFor(modelItem => artist.ArtistName)
</td>
</tr>
foreach (var album in artist.Albums)
{
foreach (var song in album.Songs)
{
if (song.SongPlays != null)
{
foreach (var songPlay in song.SongPlays)
{
<tr>
<td>
#Html.DisplayFor(a => songPlay.PlayTime)
</td>
</tr>
}
}
}
}
}
The issue with this is that I cannot sort the whole child collection by PlayTime. To solve this I then tried to get it working by skipping out the preceding foreach loops using:
foreach (var songPlay in artist.Albums.SelectMany(a => a.Songs.SelectMany(b => b.SongPlays)))
{
<tr>
<td>
#Html.DisplayFor(a => songPlay.PlayTime)
</td>
</tr>
}
This seems to work without the filter applied in the controller action, but returns a null result when the filter is applied. I have tried checking in the view if the result is null, but I could not get this to work - something like:
if (artist.Albums.Select(a => a.Songs.Select(b => b.SongPlays)) != null)
{
foreach (var songPlay in artist.Albums.SelectMany(a => a.Songs.SelectMany(b => b.SongPlays)))
{ ...
I still get a null result, so I am presuming that the null check is not doing what I was hoping it would do.
So if anyone can give me some guidance either on whether this approach is sensible and if I can do a null check on a grandchild collection somehow, or if there would be a better approach, it would be very much appreciated.

Answer 1

I'm not sure I get you right. As far as I understand you need to filter null items and second code sample in your question is ok in terms of orderting. In that case, you may add Where clause to selection:
foreach (var songPlay in artist.Albums.SelectMany(a => a.Songs.Where(b => b != null).SelectMany(b => b.SongPlays)))
{
<tr>
<td>
#Html.DisplayFor(a => songPlay.PlayTime)
</td>
</tr>
}