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POWhat am I missing in this chain of predicates?
 

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  1. POWhat am I missing in this chain of predicates?
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    <p><strong>NOTE</strong>: Right before posting this question it occurred to me there's a better way of doing what I was trying to accomplish (and I feel pretty stupid about it):</p> <pre><code>IEnumerable&lt;string&gt; checkedItems = ProductTypesList.CheckedItems.Cast&lt;string&gt;(); filter = p =&gt; checkedItems.Contains(p.ProductType); </code></pre> <p>So OK, yes, I already realize this. However, I'm posting the question anyway, because I still don't quite get why what I was (stupidly) <strong>trying</strong> to do wasn't working.</p> <hr> <p>I thought this would be extremely easy. Turns out it is giving me quite a headache.</p> <p>The basic idea: display all the items whose <code>ProductType</code> property value is checked in a <code>CheckedListBox</code>.</p> <p>The implementation:</p> <pre><code>private Func&lt;Product, bool&gt; GetProductTypeFilter() { // if nothing is checked, display nothing Func&lt;Product, bool&gt; filter = p =&gt; false; foreach (string pt in ProductTypesList.CheckedItems.Cast&lt;string&gt;()) { Func&lt;Product, bool&gt; prevFilter = filter; filter = p =&gt; (prevFilter(p) || p.ProductType == pt); } return filter; } </code></pre> <p>However, say the items "Equity" and "ETF" are both checked in <code>ProductTypesList</code> (a <code>CheckedListBox</code>). Then for some reason, the following code only returns products of type "ETF":</p> <pre><code>var filter = GetProductTypeFilter(); IEnumerable&lt;Product&gt; filteredProducts = allProducts.Where(filter); </code></pre> <p>I guessed it might have had something to do with some self-referencing messiness where <code>filter</code> is set to, essentially, itself <em>or</em> something else. And I thought that maybe using ...</p> <pre><code>filter = new Func&lt;Product, bool&gt;(p =&gt; (prevFilter(p) || p.ProductType == pt)); </code></pre> <p>...would do the trick, but no such luck. Can anybody see what I am missing here?</p>
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