Question

Given this code:

using (var conn = new SqlConnection('...')) {     conn.Open();     using (var cmd = conn.CreateCommand())     {         cmd.CommandText = '...';         using (var reader = cmd.ExecuteReader())         {             while (reader.Read())             {                 // ...             }         }     } } 

I’m used to writing try/catch/finally blocks for my data access, however, I’m being exposed to ‘using’ which seems like a much simpler method of doing this. However, I’m trying to figure out how to catch exceptions that may occur.

Could you please give me an example of how you’d catch exceptions?

Edited to add:

I’m being led to believe that ‘using’ is a replacement for my try/catch/finally blocks. I understand that using doesn’t catch exceptions. So how is this a replacement?

Answer 1

using isn’t designed to catch exceptions; it’s designed to give you an easy way to wrap a try/finally around an object that needs to be disposed. If you need to catch and handle exceptions then you’ll need to expand it into a full try/catch/finally or put a containing try/catch around the whole thing.

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To answer your edit (is using a replacement for try/catch/finally?) then no, it isn’t. Most of the time when using a disposable resource you aren’t going to handle the exception there and then because there’s normally nothing useful you can do. So it provides a convenient way to just ensure that the resource is cleaned up irrespective of what you’re trying to do works or not.

Typically code that deals with disposable resources is working at too low a level to decide what the correct action is on failure, so the exception is left to propagate to the caller who can decide what action to take (e.g. retry, fail, log, etc.). The only place where you’d tend to use a catch block with a disposable resource is if you’re going to translate the exception (which is, I assume, what your data access layer is doing).