C# "using" blocks and catching exceptions [duplicate]

Question

This question already has answers here:

try/catch + using, right syntax (9 answers)

Closed 8 years ago.

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).

Answer 1

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.

Answer 2

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