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copied!<p>So, here's the thing. There's language integrated query (Linq), and then there's yielded enumeration (a.k.a. Iterators).</p> <p>Linq allows you to define an expression tree that is later executed by something that may or may not be C# (for example the expression could be translated into a SQL query). If you're writing linq there is a good chance your query provider (the thing that does the expression translation) does not support exception handling (much less whatever you're doing that throws exceptions).</p> <p>Interators on the other hand (or "linq to objects") just ends up executing in C#, so you can just go wild with your exception handling.</p> <p>For example w/ linq to objects you can do this:</p> <pre><code>var myList = new[] { "1", "2", "BARF", "3" }; var sum = myList.Select(str => { try { return Int32.Parse(str); } catch { return 0; } }).Aggregate((x, y) => x + y); </code></pre> <p>If you're indeed doing linq to objects, and you just want to skip elements where your source IEnumerable threw an exception check out Vladimir Gondarev's answer.</p> <p>The important thing to understand however, is that the anonymous function we just passed to that Select call <strong>is not an Expression (an uncompiled expression tree)</strong>, it is a Func (a delegate pointing to compiled c# code), which means that it will run in the .Net process, even if we replaced myList with a linq to entities table (or some other linq provider). The reason for this is that the C# expression syntax does not support blocks, nor does it support try-catch. Unsurprisingly, given that, the SQL-style Linq statements (from xxx select yyy) also do not support try-catch blocks.</p> <p>However, just because the C# expression syntax doesn't support it doesn't mean you can't do it. But, to be clear, <strong>I do not recommend doing this</strong> because I highly doubt there is a QueryProvider in existence that supports it (aside from the linq to objects provider). For the curious here's how you would create a lambda expression that contains a try-catch block.</p> <pre><code>var parseMethod = typeof(Int32).GetMethod("Parse", new[] { typeof(String) }); var param = Expression.Parameter(typeof(String)); var selectExp = Expression.Lambda<Func<String, Int32>>( Expression.TryCatch( Expression.Call(parseMethod, param), Expression.Catch(typeof(Exception), Expression.Constant(0)) ), param ); var sum = myList.Select(selectExp).Aggregate((x, y) => x + y); </code></pre> <p>So when somebody implements a QueryProvider backed by a store that supports exception handling, you could use this.</p>

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