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POrefactor LINQ TO SQL custom properties that instantiate datacontext
 

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  1. POrefactor LINQ TO SQL custom properties that instantiate datacontext
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    <p>I am working on an existing ASP.NET MVC app that started small and has grown with time to require a good re-architecture and refactoring.</p> <p>One thing that I am struggling with is that we've got partial classes of the L2S entities so we could add some extra properties, but these props create a new data context and query the DB for a subset of data. This would be the equivalent to doing the following in SQL, which is not a very good way to write this query as oppsed to joins: </p> <pre><code>SELECT tbl1.stuff, (SELECT nestedValue FROM tbl2 WHERE tbl2.Foo = tbl1.Bar), tbl1.moreStuff FROM tbl1 </code></pre> <p>so in short here's what we've got in some of our partial entity classes:</p> <pre><code>public partial class Ticket { public StatusUpdate LastStatusUpdate { get { //this static method call returns a new DataContext but needs to be refactored var ctx = OurDataContext.GetContext(); var su = Compiled_Query_GetLastUpdate(ctx, this.TicketId); return su; } } } </code></pre> <p>We've got some functions that create a compiled query, but the issue is that we also have some DataLoadOptions defined in the DataContext, and because we instantiate a new datacontext for getting these nested property, we get an exception </p> <blockquote> <p>"Compiled Queries across DataContexts with different LoadOptions not supported"</p> </blockquote> <p>. The first DataContext is coming from a DataContextFactory that we implemented with the refactorings, but this second one is just hanging off the entity property getter.</p> <p>We're implementing the Repository pattern in the refactoring process, so we <strong>must</strong> stop doing stuff like the above. Does anyone know of a good way to address this issue?</p> <p>EDIT: I am adding the code for the DataContextFactory that we created during our refactoring efforts. Note that in the code above we have a GetContext() static method in the Linq DataContext class, which news up a datacontext, and is not using the DataContextFactory below:</p> <pre><code>public class DataContextFactory&lt;T&gt; : IDataContextFactory where T : System.Data.Linq.DataContext { public DataContextFactory() { _context = Activator.CreateInstance&lt;T&gt;(); } public DataContextFactory(T context) { _context = context; } private System.Data.Linq.DataContext _context; public System.Data.Linq.DataContext Context { get { return _context; } } public void SaveAll() { Context.SubmitChanges(); } public bool IsContextDirty { get { return Context != null &amp;&amp; (Context.GetChangeSet().Deletes.Count &gt; 0 || Context.GetChangeSet().Inserts.Count &gt; 0 || Context.GetChangeSet().Updates.Count &gt; 0); } } } </code></pre>
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    1. USThiago Silva
    1. USThiago Silva
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      1. POrefactor LINQ TO SQL custom properties that instantiate datacontext
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    1. CObtw, a little more info so I don't get people answering to the wrong problem. I understand why we are getting the LoadOptions exception, and we've addressed this by making the assignment of LoadOptions a static delegate call immediatelly when the DataContext is loaded. The main issue is that we actually have 2 separate contexts, and due to new implementation of a repository pattern, we need to somehow make these properties to be able to utilize the same context that is created by the DataContextFactory from the Repository.
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      1. USThiago Silva
    2. CODoes the DataContextFactory instantiate a new DataContext each time GetContext is called?
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      1. USPeter Willis
    3. CO@SteadyEddi - I've edited my original post with the code for the DataContextFactory. So to answer your question, the GetContext() method is not in the factory, but rather in the DataContext class. And it does instantiate a new context everytime. However, the factory class will save the context into a private field, as long we hang on to the factory instance throughout the lifetime of the web request (since this is for an ASP.NET MVC app).
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