C# How to convert SQL into a LINQ query

Question

I have a WinForms application connected to a Movies SQL Server database via Entity Framework (EF 6).

I have the following SQL which I'm attempting to convert into a LINQ query

SELECT 
    t.movieId,m.Title, t.number_of_files 
FROM 
    (SELECT mlf.movieId AS movieId, COUNT(*) AS number_of_files
     FROM MovieLinkFile mlf, "file" f
     WHERE f.path LIKE 'M:\%'
       AND f.id = mlf.fileId
     GROUP BY mlf.movieId
     HAVING COUNT(*) > 1) t
JOIN 
    Movie m ON t.movieId = m.Id
ORDER BY 
    m.title

Here is my attempt at LINQ using LINQPad http://www.linqpad.net/

from m in Movies
from mlf in Movielinkfiles
from f in Files
where m.Id == mlf.MovieId
      &&  mlf.FileId == Files.id
      && f.path.StartsWith ("M:\\")
.GroupBy(x =>  x.movieId)
.where(c => c.count()  > 1)  // invalid expression
select m

The C# code for connecting to the DB looks something like this

private void LoadMovies()
{
    TitlesLV.Items.Clear();

    using (var context = new MoviesEntities())
    {
        // get a full list of all movies (will return everything from the database)
        var allMovies = context.movies.OrderBy(m => m.title).ToArray();

        foreach(var Movie in allMovies)
        {
            ListViewItem item = new ListViewItem();
            item.Text = Movie.title;
            item.Tag = Movie;

            TitlesLV.Items.Add(item);
        }
    }
}

In the database there are 3 tables:

• Movies (id, Title, Year, IMDB,etc)
• MoviesLinkFiles (id, MovieId, FileId)
• Files (id, path)

How do I write the LINQ statement in C#?

Answer 1

To get all movies that have more than one file starting with "M:\", use Count with the Path.StartsWith expression, and check the result of Count is greater than 1.

var filteredMovies = movies
    .Where(movie => movie.Files
        .Count(file => file.Path.StartsWith("M:\\")) > 1
    )
    .OrderBy(movie => movie.Title);