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    <blockquote> <p>does it create and open new connection every time? </p> </blockquote> <p>No. Connections are cached.</p> <blockquote> <p>Should I cache the results somewhere</p> </blockquote> <p>No. Do not cache entire tables.</p> <blockquote> <p>should I make TicDatabaseEntities variable static and initialize it at class level? </p> </blockquote> <p>No. Do not retain a DataContext instance longer than a UnitOfWork.</p> <blockquote> <p>Should my class be static if it contains only static methods?</p> </blockquote> <p>Sure... doing so will prevent anyone from creating useless instances of the class.</p> <blockquote> <p>Also I've noticed that if I return result.First() instead of FirstOrDefault() and the query does not find a match, it will issue an exception</p> </blockquote> <p>That is the behavior of First. As such - I typically restrict use of First to IGroupings or to collections previously checked with .Any().</p> <hr> <p>I'd rewrite your existing method as:</p> <pre><code>using (TicDatabaseEntities db = new TicDatabaseEntities()) { bool result = db.Articles .Any(a =&gt; a.supplierArticleID.Equals(supplierIdent)); return result; } </code></pre> <p>If you are calling the method in a loop, I'd rewrite to:</p> <pre><code>private static Dictionary&lt;string, bool&gt; TicArticleExists (List&lt;string&gt; supplierIdents) { using (TicDatabaseEntities db = new TicDatabaseEntities()) { HashSet&lt;string&gt; queryResult = new HashSet(db.Articles .Where(a =&gt; supplierIdents.Contains(a.supplierArticleID)) .Select(a =&gt; a.supplierArticleID)); Dictionary&lt;string, bool&gt; result = supplierIdents .ToDictionary(s =&gt; s, s =&gt; queryResult.Contains(s)); return result; } } </code></pre>
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    1. POEntity framework with Linq to Entities performance
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    1. USAmy B
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    1. COvery nice, thank you!
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      1. USmare
    2. COAfter accepting your answer, I found out that the first piece of code you provided (using Any()) takes much longer to execute vs my previous code based on Count(). The second method has some issue too - specifically it timeouts when making the HashSet.
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    3. COUse db.Log = Console.Out; to dump out the query used. Find the difference in the query.
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