Lambda expression select Count from virtual ICollection

Question

i have an trouble with lambda expression i have some releated tables and i need to select some results with count and avarage functions here ise the example class

class Course{
public long id;
public string name;
public virtual ICollection<Chapter> chapters;
}

class Chapter{
public long id;
public virtual ICollection<Videos> videos;
public virtual ICollection<Files> files;
}

i need to select them into

select new{
videoCount = [number of video releated to course],
fileCount = [number of file releated to course],
}

how can i select with lambda expression like

var result = from c in Courses...
             i cant figured out here
             select new{
                          videoCount = [number of video releated to course],
                          fileCount = [number of file releated to course],
             };

thanks for your help.

Blockquote

Could you show us your Videos and Files class too?

KRONWALLED
– KRONWALLED

2016-06-10 13:52:20 +00:00
Commented Jun 10, 2016 at 13:52 — KRONWALLED
– KRONWALLED, Commented Jun 10, 2016 at 13:52

Alberto Chiesa · Accepted Answer · 2016-06-10 13:55:28Z

2

You have an error in your code: after public virtual ICollection<Chapter> you don't have the property name. I assume it is called Chapters. Same for Videos and Files properties.

Try this:

var result = courses.Select(c => new
{
    videoCount = c.chapters.Sum(chapter => chapter.Videos.Count()),
    fileCount = c.chapters.Sum(chapter => chapter.Files.Count())
});

You Sum the count of videos in each chapter, to get the total for the course.

answered Jun 10, 2016 at 13:55

Alberto Chiesa

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Comments

Tamas Ionut · Accepted Answer · 2016-06-10 13:55:14Z

0

Try this:

var courses = new List<Course>();

courses.Select(x=> new { 
                       VideoCount = x.Chapters.Sum(v=>v.Videos.Count),
                       FilesCount = x.Chapters.Sum(v=>v.Files.Count)
                       });

answered Jun 10, 2016 at 13:55

Tamas Ionut

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