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    <p>First of all I'd like to point out that key-value pairs (AKA EAV model) are a poor choice for representing this kind of data, and this question is a perfect example of why - it's much, much harder to search for arbitrary collections of attributes than it is to search for specific properties.</p> <p>Of course, it can still be done:</p> <pre><code>var suitableProducts = from p in products where p.Items.Any(s =&gt; s.Key == "dental" &amp;&amp; s.Value == "true") &amp;&amp; p.Items.Any(s =&gt; s.Key == "therapies" &amp;&amp; s.Value == "false") select p; </code></pre> <p>It's just not as easy to write or efficient as querying on a <code>Product</code> class that actually has <code>dental</code> and <code>therapies</code> properties as opposed to nested attributes.</p> <p>If you the number of items you need to <em>query on</em> can change, then the easiest way to handle that is to chain together filters:</p> <pre><code>var searchItems = ... var result = products; foreach (var searchItem in searchItems) { result = result.Where(p =&gt; p.Items.Any(s =&gt; s.Key == searchItem.Key &amp;&amp; s.Value == searchItem.Value)); } // Do something with result </code></pre> <p>If you're looking for a more "functional" way to do it without chaining then:</p> <pre><code>var suitabilityConditions = searchItems.Select(i =&gt; (Predicate&lt;Product&gt;)(p =&gt; p.Items.Any(s =&gt; s.Key == searchItem.Key &amp;&amp; s.Value == searchItem.Value))); Predicate&lt;Product&gt; match = p =&gt; suitabilityConditions.All(c =&gt; c(p)); var suitableProducts = products.Where(match); </code></pre>
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    1. CO@Aaronaught, thanks for this but I can't code each line like you have. I may be given 2 items or 10. As for the approach (EAV) what model would you suggest where each product has a variable number of items attached to it?
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    2. CO@griegs: Added a version for a dynamic number of items. As for what I would suggest - I would suggest not having a design where each product can have arbitrary sets of attributes. Such designs are anti-patterns, and may *sometimes* be necessary but are usually the result of a combination of vague requirements and a desire to lower maintenance costs through end-user customization. Know that it will actually raise TCO due to myriad issues like this (another issue being that attributes are weakly-typed - what happens if you want to sort?); better to fix the vague requirements instead.
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    3. COI hear you and this was discussed but the boss pointed out that we need a way to change the number of items associated to a product to accommodate the businesses changes of mind on a monthly basis.
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