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POWhy catch and rethrow an exception in C#?
 

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  1. POWhy catch and rethrow an exception in C#?
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    <p>I'm looking at the article <em><a href="http://www.codeproject.com/KB/cs/datatransferobject.aspx" rel="noreferrer">C# - Data Transfer Object</a></em> on serializable DTOs.</p> <p>The article includes this piece of code:</p> <pre><code>public static string SerializeDTO(DTO dto) { try { XmlSerializer xmlSer = new XmlSerializer(dto.GetType()); StringWriter sWriter = new StringWriter(); xmlSer.Serialize(sWriter, dto); return sWriter.ToString(); } catch(Exception ex) { throw ex; } } </code></pre> <p>The rest of the article looks sane and reasonable (to a noob), but that try-catch-throw throws a WtfException... <strong>Isn't this exactly equivalent to not handling exceptions at all?</strong></p> <p>Ergo:</p> <pre><code>public static string SerializeDTO(DTO dto) { XmlSerializer xmlSer = new XmlSerializer(dto.GetType()); StringWriter sWriter = new StringWriter(); xmlSer.Serialize(sWriter, dto); return sWriter.ToString(); } </code></pre> <p>Or am I missing something fundamental about error handling in C#? It's pretty much the same as Java (minus checked exceptions), isn't it? ... That is, they both refined C++.</p> <p>The Stack Overflow question <em><a href="https://stackoverflow.com/questions/717489">The difference between re-throwing parameter-less catch and not doing anything?</a></em> seems to support my contention that try-catch-throw is-a no-op.</p> <hr> <p><strong>EDIT:</strong></p> <p>Just to summarise for anyone who finds this thread in future...</p> <p><strong>DO NOT</strong></p> <pre><code>try { // Do stuff that might throw an exception } catch (Exception e) { throw e; // This destroys the strack trace information! } </code></pre> <p>The stack trace information can be crucial to identifying the root cause of the problem!</p> <p><strong>DO</strong></p> <pre><code>try { // Do stuff that might throw an exception } catch (SqlException e) { // Log it if (e.ErrorCode != NO_ROW_ERROR) { // filter out NoDataFound. // Do special cleanup, like maybe closing the "dirty" database connection. throw; // This preserves the stack trace } } catch (IOException e) { // Log it throw; } catch (Exception e) { // Log it throw new DAOException("Excrement occurred", e); // wrapped &amp; chained exceptions (just like java). } finally { // Normal clean goes here (like closing open files). } </code></pre> <p>Catch the more specific exceptions before the less specific ones (just like Java).</p> <hr> <p><strong>References:</strong></p> <ul> <li><a href="http://msdn.microsoft.com/en-us/library/ms229005.aspx" rel="noreferrer">MSDN - Exception Handling</a></li> <li><a href="http://msdn.microsoft.com/en-us/library/0yd65esw.aspx" rel="noreferrer">MSDN - try-catch (C# Reference)</a></li> </ul>
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    1. COGood summary; extra points for including the finally block.
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      1. POWhy catch and rethrow an exception in C#?
      1. USFredrik Mörk
    2. COi would like to add that you can use the "throw;" to be even more helpful by adding the parameters that were sent to the method in the e.Data collection before the "throw;" statement
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      1. POWhy catch and rethrow an exception in C#?
      1. USMichael Bahig
    3. CO@MickTheWarMachineDesigner (and part-time painter). Huh? You're talking handling Microshite Suckwell (proabably 2005 onwards, for all I know) exceptions. I was talking about exception handling in general. And yes I've learned some since I posted this NEARLY FOUR YEARS AGO.... But yes, I confess that you have valid point, but me thinks you've missed the real point; if you get my drift? This question is about GENERALISED exception handling in C#; and more specifically about rethrowing exceptions... of ALL kinds. Cool?
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