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POLinq throws exception on .Substring()
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  1. POLinq throws exception on .Substring()
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    copied!<p>I've got a situation where I need to have my LINQ to Entities query return a substring depending on the length of the string. Here's the Query:</p> <pre><code>var query = ( from f in Context.Files orderby f.DateAdded descending select new { Concerns = f.Concerns.Name, Sender = f.Sender.Name, CategoryCount = f.Categories.Count(), DateAdded = f.DateAdded, Comment = (f.Comment == null || f.Comment.Length &lt; 5) ? f.Comment : f.Comment }).Take(10); </code></pre> <p>So what I'm doing is getting the last 10 added Entities of type Files and then select a set of properties from it to display inside a listview. Some are plain strings (Concerns, Sender). CategoryCount returns the number of categories which are associated with the File object.</p> <p>However, I want the comment to be truncated if it is longer then a given length. In the above code, everything is working correctly. Now when I replace this line:</p> <pre><code>Comment = (f.Comment == null || f.Comment.Length &lt; 5) ? f.Comment : f.Comment </code></pre> <p>With this line:</p> <pre><code>Comment = (f.Comment == null || f.Comment.Length &lt; 5) ? f.Comment : f.Comment.SubString(0,5) </code></pre> <p>the application throws a XamlParseException (???)</p> <blockquote> <p>The invocation of the constructor on type 'DocumentManager.Views.ListEntriesView' that matches the specified binding constraints threw an exception</p> </blockquote> <p>I really don't know why it would do that. Is the SubString method not supported in LINQ?</p> <p>Hope someone can help me here. Until then, I'll just leave it the way it is.</p> <p>EDIT 2 (Somehow, my first edit got lost. So I'm redoing it): Based on the comments I got I changed my code to this and it works now:</p> <pre><code>var query = App.Context.Files.OrderByDescending(File =&gt; File.DateAdded).Take(10).AsEnumerable() .Select(File =&gt; new { Concerns = File.Concerns.Name, Sender = File.Sender.Name, CategoryCount = File.Categories.Count(), DateAdded = File.DateAdded, Comment = (File.Comment == null || File.Comment.Length &lt; 100) ? File.Comment : File.Comment.Substring(0, 100) + "..." }); </code></pre> <p>I forgot to mention that I'm using SQLite. So maybe Substring is not implemented in the SQLite EF Provider.</p>
 

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