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POQuery or algorithm to generate a structure to populate a tree (C#, LINQ)
 

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  1. POQuery or algorithm to generate a structure to populate a tree (C#, LINQ)
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    <p>I couldn't find or come up with a generic and elegant algorithm that would let me populate the tree-like structure. The simplest example is a blog archive: I have a bunch of records which can be selected and sorted by date. I want to have a tree where years may be top level, months are next level and actual post titles are next again.</p> <p>So far I've came up with a naive straight forward implementation that works, but I'm sure that could be improved using LINQ, etc. Here I just sort records by date and iterate checking if the year or month has changed, and add tree nodes accordingly. "BlogEntry" is a class that has a reference to both a parent and children and is later used to generate HTML.</p> <p>I welcome suggestions on improving the algorithm!</p> <pre><code>IEnumerable&lt;Post&gt; posts = db.Posts.OrderBy(p =&gt; p.DateCreated); var topPost = posts.First(); int curYear = topPost.DateCreated.Year; int curMonth = topPost.DateCreated.Month; //create first "year-level" item var topYear = new BlogEntry { Name = topPost.DateCreated.Year.ToString().ToLink(string.Empty) }; entries.Add(topYear); var currentYear = topYear; var topMonth = new BlogEntry { Name = topPost.DateCreated.ToString("MMMM").ToLink(string.Empty), Parent = currentYear }; currentYear.Children.Add(topMonth); var currentMonth = topMonth; foreach (var post in posts) { if(post.DateCreated.Year == curYear) { if (post.DateCreated.Month != curMonth) { //create "month-level" item var month = new BlogEntry { Name = post.DateCreated.ToString("MMMM").ToLink(string.Empty), Parent = currentYear }; currentYear.Children.Add(month); currentMonth = month; curMonth = post.DateCreated.Month; } //create "blog entry level" item var blogEntry = new BlogEntry { Name = post.Title.ToLink("/Post/" + post.PostID + "/" + post.Title.ToSeoUrl() ), Parent = currentMonth }; currentMonth.Children.Add(blogEntry); } else { //create "year-level" item var year = new BlogEntry { Name = post.DateCreated.Year.ToString().ToLink(string.Empty) }; entries.Add(year); currentYear = year; curMonth = post.DateCreated.Month; curYear = post.DateCreated.Year; } } </code></pre>
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    1. COHave you tried using Resharper? It can automatically convert simple loops to LINQ code. [I'm not affiliated with Resharper in any form :)]
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    2. COWhat are you trying to improve? Performance? Maintainability? Code elegance?
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    3. COMaybe you're looking for something like this? http://stackoverflow.com/questions/2230202/how-can-i-hierarchically-group-data-using-linq
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      1. USChris Sinclair
 

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