C# "using" blocks and catching exceptions

Question

I have this code:

using (var requestStream = request.GetRequestStream())
{
    byte[] data = Encoding.UTF8.GetBytes(xmlData);
    requestStream.Write(data, 0, data.Length);
}

If the request I'm making fails because the remote server is down, how do I catch the error?

Should I just expand out the using block to try-catch-finally, or is there a more elegant way this is done when using "using" blocks?

(I need to catch only server-being-down type errors this way - I need to show the client these errors happen because their server connection is inadequate, not because of bugs in our software or something).

http://stackoverflow.com/questions/4590490/try-catch-using-right-syntax — devnull, Jun 05 '13 at 06:26

score 7 · Accepted Answer · answered Jun 05 '13 at 06:22

There are definitely four options here:

Abandon using and just have a try/catch/finally:

var requestStream = request.GetRequestStream();
try
{
    byte[] data = Encoding.UTF8.GetBytes(xmlData);
    requestStream.Write(data, 0, data.Length);
}
catch (IOException e) // Or whatever
{
    // Whatever you want
}
finally
{
    requestStream.Dispose();
}

Put just a try/catch block inside the using block:

using (var requestStream = request.GetRequestStream())
{
    try
    {
        byte[] data = Encoding.UTF8.GetBytes(xmlData);
        requestStream.Write(data, 0, data.Length);
    }
    catch (IOException e) // Or whatever
    {
        // Whatever you want
    }
}

The same as the second option, but with the try/catch outside the using block instead of inside. I don't think it makes much difference which you use, to be honest.
Catch the exception at a higher level anyway, e.g. in the calling method. Often this is a better approach, as you may well want to handle one type of exception from multiple "small" operations in the same way from the perspective of the "larger" operation.

Personally I generally favour the second approach or the fourth. It's a consistent change: when I want to catch an exception, I introduce a try/catch block. The fact that it happens to be inside a using statement is neither here nor there. It ends up with more nesting, but I find it happens rarely enough that that's not a problem.

Or perhaps, many *smaller* exceptions in different ways from different (new) callers. — jpaugh, Jun 05 '13 at 18:12

jspcal · Answer 2 · 2013-06-05T07:24:32.640

1

The using statement will still throw an exception if the initialization fails, so you can wrap it in your own try/catch block.

edited Jun 05 '13 at 07:24

answered Jun 05 '13 at 06:21

jspcal

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I think you mean try/catch rather than try/finally. – Jon Skeet Jun 05 '13 at 06:26

C# "using" blocks and catching exceptions

2 Answers2