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POOptimizing an algorithm and/or structure in C#
 

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  1. POOptimizing an algorithm and/or structure in C#
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    <p>I'm working on an application where you're able to subscribe to a newsletter and choose which categories you want to subscribe to. There's two different sets of categories: cities and categories.</p> <p>Upon sending emails (which is a scheduled tast), I have to look at which cities and which categories a subscriber has subscribed to, before sending the email. I.e., if I have subscribed to "London" and "Manchester" as my cities of choice and have chosen "Food", "Cloth" and "Electronics" as my categories, I will only get the newsletters that relates to these.</p> <p>The structure is as follows:</p> <p>On every newsitem in Umbraco CMS there is a commaseparated string of cities and categories (effectively, these are stored as node ids since cities and categories are nodes in Umbraco aswell) When I subscribe to one or more city and one or more category, I store the city and category nodeids in the database in custom tables. My relational mapping looks like this:</p> <p><img src="https://i.stack.imgur.com/fzU97.png" alt="enter image description here"></p> <p>And the whole structure looks like this:</p> <p><img src="https://i.stack.imgur.com/HELhQ.png" alt="enter image description here"></p> <p>To me, this seems like two sets of 1 - 1..* relations (one subscriber to one or many cities and one subscriber to one or many categories)</p> <p>To find which emails to send who which subscriber, my code looks like this:</p> <pre><code>private bool shouldBeAdded = false; // Dictionary containing the subscribers e-mail address and a list of news nodes which should be sent Dictionary&lt;string, List&lt;Node&gt;&gt; result = new Dictionary&lt;string, List&lt;Node&gt;&gt;(); foreach(var subscriber in subscribers) { // List of Umbraco CMS nodes to store which nodes the html should come from List&lt;Node&gt; nodesToSend = new List&lt;Node&gt; nodesToSend(); // Loop through the news foreach(var newsItem in news) { // The news item has a comma-separated string of related cities foreach (string cityNodeId in newsItem.GetProperty("cities").Value.Split(',')) { // Check if the subscriber has subscribed to the city if(subscriber.CityNodeIds.Contains(Convert.ToInt32(cityNodeId))) { shouldBeAdded = true; } } // The news item has a comma-separated string of related categories foreach (string categoryNodeId in newsItem.GetProperty("categories").Value.Split(',')) { // Check if the subscriber has subscribed to the category if(subscriber.CategoryNodeIds.Contains(Convert.ToInt32(categoryNodeId))) { shouldBeAdded = true; } } } // Store in list if (shouldBeAdded) { nodesToSend.Add(newsItem); } // Add it to the dictionary if (nodesToSend.Count &gt; 0) { result.Add(subscriber.Email, nodesToSend); } } // Ensure that we process the request only if there are any subscribers to send mails to if (result.Count &gt; 0) { foreach (var res in result) { // Finally, create/merge the markup for the newsletter and send it as an email. } } </code></pre> <p>While this works, I'm a bit concerned about performance when a certain amount of subscribers is reached since we're into three nested foreach loops. Also, remembering my old teachers preaches: "for every for loop there is a better structure" </p> <p>So, I would like your oppinion on the above solution, is there anything that can be improved here with the given structure? And will it cause performance problems over time?</p> <p>Any help/hint is greatly appreciated! :-)</p> <p>Thanks in advance.</p> <p><strong>Solution</strong></p> <p>So after a few good hours of debugging and fumblin' around I finally came up with something that works (initially, it looked like my original code worked, but it didn't)</p> <p>Sadly, I couldn't get it to work with any LINQ queries I tried, so I went back to the "ol' school' way of iterating ;-) The final algorithm looks like this:</p> <pre><code>private bool shouldBeAdded = false; // Dictionary containing the subscribers e-mail address and a list of news nodes which should be sent Dictionary&lt;string, List&lt;Node&gt;&gt; result = new Dictionary&lt;string, List&lt;Node&gt;&gt;(); foreach(var subscriber in subscribers) { // List of Umbraco CMS nodes to store which nodes the html should come from List&lt;Node&gt; nodesToSend = new List&lt;Node&gt; nodesToSend(); // Loop through the news foreach(var newsItem in news) { foreach (string cityNodeId in newsItem.GetProperty("cities").Value.Split(',')) { // Check if the subscriber has subscribed to the city if (subscriber.CityNodeIds.Contains(Convert.ToInt32(cityNodeId))) { // If a city matches, we have a base case nodesToSend.Add(newsItem); } } foreach (string categoryNodeId in newsItem.GetProperty("categories").Value.Split(',')) { // Check if the subscriber has subscribed to the category if (subscriber.CategoryNodeIds.Contains(Convert.ToInt32(categoryNodeId))) { shouldBeAdded = true; // News item matched and will be sent. Stop the loop. break; } else { shouldBeAdded = false; } } if (!shouldBeAdded) { // The news item did not match both a city and a category and should not be sent nodesToSend.Remove(newsItem); } } if (nodesToSend.Count &gt; 0) { result.Add(subscriber.Email, nodesToSend); } } // Ensure that we process the request only if there are any subscribers to send mails to if (result.Count &gt; 0) { foreach (var res in result) { // StringBuilder to build markup for newsletter StringBuilder sb = new StringBuilder(); // Build markup foreach (var newsItem in res.Value) { // build the markup here } // Email logic here } } </code></pre>
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    1. COI have to say I don't know anything about Umbraco but I marked this question up as it is a *model* of how to go about asking such a question.
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    2. COThanks deadlyvices :) I'm aware that the above code example can (and will!) be refactored to more than one method.
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