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POModify linq query at runtime
 

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    <p><strong>Problem statement</strong></p> <p>Say I have a query which searches the names of people:</p> <pre><code>var result = (from person in container.people select person) .Where(p =&gt; p.Name.Contains(some_criterion) </code></pre> <p>This will be translated to a SQL query containing the following like clause:</p> <pre><code>WHERE NAME LIKE '%some_criterion%' </code></pre> <p>This has some performance implications, as the database is unable to effectively use the index on the name column (index scan v.s. index seek if I'm not mistaken).</p> <p>To remedy this, I can decide to just StartsWith() instead, generating a query using a like clause like:</p> <pre><code>WHERE NAME LIKE 'some_criterion%' </code></pre> <p>Which enables SQL server to use the index seek and delivering performance at the cost of some functionality.</p> <p>I'd like to be able to provide the user with a choice: defaulting the behavior to use StartsWith, but if the user want the 'added flexibility' of searching using Contains(), than that should used.</p> <p><strong>What have I tried</strong></p> <p>I thought this to be trivial and went on and implemented an extension method on string. But of course, LINQ does not accept this and an exception is thrown.</p> <p>Now, of course I can go about and use an if or switch statement and create a query for each of the cases, but I'd much rather solve this 'on a higher level' or more generically. In short: using an if statement to differentiate between use cases isn't feasible due to the complexity of the real-life application. This would lead to alot of repetition and clutter. I'd really like to be able to encapsulate the varying behavior (Contains, StartsWith, EndsWith) somehow.</p> <p><strong>Question</strong></p> <p>Where should I look or what should I look for? Is this a case for composability with IQueryables? I'm quite puzzled!</p>
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    1. COCriterium. Singular of criteria.
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    2. COThat would be "criterion".
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    3. COAha, ok. Wasn't aware. Overextending rules applying to my own language to English ;)
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