CODEWITHSUNDEEP
c#linq
James South
James South

Reputation: 10635

Group and count Dictionary Items

I have a Dictionary<string, CachedImage> with which I'd like to group the items, count the number of items in the group and iterate through each group if the count is greater than 6500.

The CachedImage class contains Path And ExpiresUtc properties that I am interested in.

My Linq-fu is sadly lacking with complex queries so this is as far as I have got and I think I've already messed up. I'm assuming what I want is possible.

Any help would be appreciated, especially with a quick walkthrough.

Regex searchTerm = new Regex(@"(jpeg|png|bmp|gif)");
var groups= PersistantDictionary.Instance.ToList()
            .GroupBy(x => searchTerm.Match(x.Value.Path))
            .Select(y => new
                           {
                            Path = y.Key,
                            Expires = y.Select(z => z.Value.ExpiresUtc),
                            Count = y.Sum(z => z.Key.Count())
                           })
            .AsEnumerable();

Upvotes: 1

Views: 1710

Answers (1)

nick_w
nick_w

Reputation: 14938

Try this:

var groups = PersistantDictionary.Instance.ToList()
        .GroupBy(x => searchTerm.Match(x.Value.Path).Value)
        .Where(g => g.Count() > 6500);

foreach (var group in groups)
{
    Console.WriteLine("{0} images for extension {1}", group.Count(), group.Key);

    foreach (KeyValuePair<string, CachedImage> pair in group)
    {
        //Do stuff with each CachedImage.
    }
}

So to break this down:

PersistantDictionary.Instance.ToList()

Produces a list of KeyValuePair<string, CachedImage>.

.GroupBy(x => searchTerm.Match(x.Value.Path).Value)

Groups the list by the Regex match against the Path of the CachedImage. Note that I have used the Value property - the Match method returns a Match object, so it would be best to group by the actual text of the match. The outcome of this step will be an IEnumerable of <IGrouping<string, KeyValuePair<string, CachedImage>>>.

.Where(g => g.Count() > 6500);

This ensures that only those groups with > 6500 items will be retrieved.

Upvotes: 2

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