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POC# lambda IN clause error
 

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    <p>I’m having issues creating an IN clause using C# and lambdas.</p> <p>I have the following method <code>GetUserList(string filtersByRoles)</code></p> <p>The variable <code>string filtersByRoles</code> can hold a comma-delimited value such as: “1,2” or “1,2,3” or “1,3,4” etc...each number represents the unique number of a Role (in other words, RoleId).</p> <p>I then have the following C# lambda query:</p> <pre><code>var query = _userRepository.GetUserList(); </code></pre> <p>Which returns an <code>IQueryable&lt;User&gt;</code> where <code>User</code> is a table from my EntityFramework.</p> <p>Once I verify if the <code>filtersByRoles</code> parameter is not null-or-empty, I need to make an <code>IN</code> clause such as:</p> <pre><code>if (!string.IsNullOrEmpty(filtersByRoles)) { //Convert *filtersByRoles* to an array of integers int[] myArray = filtersByRoles.Split(',').Select(x =&gt; int.Parse(x)).ToArray(); //Make the IN clause query = query.Where(u =&gt; myArray.Contains(u.RoleId)); } </code></pre> <p>The above code compiles...but at RUNTIME it fails with the following error message:</p> <blockquote> <p>LINQ to Entities does not recognize the method 'Boolean Contains[Int32](System.Collections.Generic.IEnumerable`1[System.Int32], Int32)' method, and this method cannot be translated into a store expression.</p> </blockquote> <hr> <p>I’ve manage to find a workaround but it involves making a call to the <code>.ToList()</code> method which I believe fetches all the data from my database and then, adds a Where() clause. But wouldn’t that defeat the purpose or create some performance issues?</p> <p>This is what I’ve done:</p> <pre><code>if (!string.IsNullOrEmpty(filtersByRoles)) { string[] myArray = filtersByRoles.Split(','); query = query.ToList().Where(u =&gt; myArray.Contains(u.RoleId.ToString())).AsQueryable(); } </code></pre> <p>I would prefer <em>not</em> to make the <code>.ToList()</code> call and avoid fetching all the data.</p> <p>Is there another way to achieve this?</p> <p>EDIT: I'm using Entity Framework 1.0 and .NET Framework 3.5</p> <p>Thanks Sincerely </p> <p>Vince</p>
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    1. COWhat version of .NET are you using?
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    2. COCrap...sorry about that...Framework 3.5 not 4.0 :-(
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    3. COThe error is telling you that the linq optimizer doesn't know how to translate Contains to a corresponding procedure in sql. I've never tried this but could you build up multiple Where's and chain them together? Like .Where( u=> u.RoleId == myArray[0] ).Where( u => u.RoleId == myArray[1]) ...
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      1. USBrian Dishaw
 

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