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POEntity Framework - Querying from ObjectContext vs Querying from Navigation Property
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  1. POEntity Framework - Querying from ObjectContext vs Querying from Navigation Property
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    copied!<p>I've noticed that depending on how I extract data from my Entity Framework model, I get different types of results. For example, when getting the list of employees in a particular department:</p> <p>If I pull directly from ObjectContext, I get an <code>IQueryable&lt;Employee&gt;</code>, which is actually a <code>System.Data.Objects.ObjectQuery&lt;Employee&gt;</code>:</p> <pre><code>var employees = MyObjectContext.Employees.Where(e =&gt; e.DepartmentId == MyDepartment.Id &amp;&amp; e.SomeCondtition) </code></pre> <p>But if I use the Navigation Property of MyDepartment, I get an <code>IEnumerable&lt;Employee&gt;</code>, which is actually a <code>System.Linq.WhereEnumerableIterator&lt;Employee&gt;</code> (private class in System.Linq.Enumerable):</p> <pre><code>var employees = MyDeparment.Employees.Where(e =&gt; e.SomeCondtition) </code></pre> <p>In the code that follows, I heavily use <code>employees</code> in several LINQ queries (<code>Where</code>, <code>OrderBy</code>, <code>First</code>, <code>Sum</code>, etc.)</p> <p><strong>Should I be taking into consideration which query method I use? Will there be a performance difference? Does the latter use deferred execution? Is one better practice? Or does it not make a difference?</strong></p> <p>I ask this because since installing ReShaper 6, I'm getting lots of <em>Possible multiple enumeration of IEnumerable</em> warnings when using the latter method, but none when using direct queries. I've been using the latter method more often, simply because it's much cleaner to write, and I'm wondering if doing so has actually had a detrimental effect!</p>
 

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