Question

I need to create a nested listview and found a great article on how to do it, but my situation is a bit different. I am a linq newbie and need a little help please 🙂

I need to get my data into a format similar in that article to work (on that link above, search for "Configuring the ListView" and see table right above it).

Here is my data:

Format    Movie Name    Price
DVD       Star Wars     12.99
DVD       Star Wars II  13.99
Blue-Ray  Star Wars     15.99
Blue-Ray  Star Wars II  17.99

Here is what I have, which isn’t really that close, but it is as far as I could get:

var MoviesToBuy = from Movie in dtMovieListDetails.AsEnumerable()
                    //join MovieDetails in dtMovieListDetails.AsEnumerable() on (string)Movie["ID"] equals (string)MovieDetails["ID"]
                    group Movie by new
                    {
                        Format = Movie["Format"],
                        Movies = Movie
                    } into grp

                    select new
                    {
                        Format = (string)grp.Key.Format,
                        Movies = grp.Key.Movies
                    };

        MoviesToBuy = MoviesToBuy.OrderBy(p => p.Format);

        lvwAmazonMovieGroup.DataSource = MoviesToBuy.ToList();
        lvwAmazonMovieGroup.DataBind();

I have 3 specific issues/questions:

1.) What I have doesn’t work. Since my second column in the group equates to all rows, no actual group is created.

2.) Despite prior issue, I am also getting "Data source is an invalid type. It must be either an IListSource, IEnumerable, or IDataSource" error. In this case, the Movies column is being created as a DataRow datatype. Not sure if that is what is creating the problem. Can I cast on that field somehow?

3.) how can I sort on the fields in the movies. I.e. in the end I want the data to be sorted by Format then Movie Name so the nested list view looks like this:

Blue-Ray
   Star Wars    12.99
   Star Wars II 13.99

DVD
   Star Wars    15.99
   Star Wars II 17.99

Any points are greatly appreciated!

Thanks in advance,
Chad

Answer 1

I was thinking you could start with the following, adjusting for the proper variable names and AsEnumerable(), etc.

It orders your movies as you want and puts them in a nested structure as you requested:

var moviesToBuy = from movie in dtMovieListDetails
    orderby movie.Format, movie.Price
    group movie by movie.Format into grp
    select new
    {
        Format = grp.Key,
        Movies = grp.Select (g => new { MovieName = g.MovieName, Price = g.Price })
    };

Here’s an example program that implements the above query.