Question

Say I had a class:

public class Post
{
    public int PostId { get; set; }
    public string Topic { get; set; }
    public int UserId { get; set; }
    [StringLength(5000)]
    public string Body { get; set; }
    public DateTime DateCreated { get; set; }
    public string Name { get; set; }
    public int Votes { get; set; }
} 

And for each post, a user could input a topic. for example, if the topics were “Red” “Green” “Blue” and “Yellow”, how could I create a list based on how many times those were used?

An example output:

Red   | 70
Blue  | 60
Green | 40
Yellow| 35

EDIT: How come this doesn’t work and gives me an error where I cannot implicitly convert the type?

public List<string> GetPopularTopics(int count)
    {
        var posts = from p in db.Posts
                    group p by p.Topic into myGroup
                    select new
                    {
                        Topic = myGroup.Key,
                        Count = myGroup.Count()
                    };
        return posts.ToList();
    }

EDIT 2:

So I tried your solution out Dustin, and I’m getting an error. This is what I used:

public IEnumerable<IGrouping<string,int>> GetPosts()
    {
        var posts = from p in db.Posts
                    group p by p.Topic into topicCounts
                    select new
                    {
                        Topic = topicCounts.Key,
                        Count = topicCounts.Count()
                    };
        return posts.ToList();
    }

This is giving me an error under posts.ToList():
Cannot implicitly convert type ‘System.Collections.Generic.List’ to ‘System.Collections.Generic.IEnumerable>’. An explicit conversion exists (are you missing a cast?)

Answer 1

You must create a new type if you do a projection and return it form method!

public class MyCounts
{
    public string Topic { get; set; }
    public int Count { get; set; }
}


public List<MyCounts> GetPopularTopics(int count)
{
    var posts = from p in db.Posts
                group p by p.Topic into myGroup
                select new MyCounts
                {
                    Topic = myGroup.Key,
                    Count = myGroup.Count()
                };
    return posts.ToList();
}