如何在FileStream.Close / Dispose上处理IOException

Question

Based on documentation FileStream.Close/Dispose can throw an IOException, with other streams/services I have switched away from 'using' due to the situation of exceptions on close leaving the connection open and essentially orphaned in favor of the following model: this decision is supported by MSDN Suggested Practice

try 
{
  //do work
  handler.Close(); //or equivalent
}
catch(IOException)
{
  handler.Abort();  
}
finally
{
  handler.Dispose(); 
}

The issue here is that on FileStream Close is essentially Dispose, and there is no Abort. This is in a project that does not have access to .net 4.5 so manually triggering the task cancellation on ReadAsync is not available, so what is the best strategy for handling this, or can you explain why this is not actually a concern unlike a connection to SQL/WCF/etc if that is actually the case?

The use case in this scenario is user image upload to a Silverlight control. I am currently using 'using' as it is more concise/readable than the t/c/f block which, in this situation, does not add any value that I can find.

Answer 1

Until today I didn't know that FileStream.Dispose/Close could throw an IOException, but it turns out it can. Not that I thought the OP was wrong.

else {
    // ERROR_INVALID_PARAMETER may be returned for writes
    // where the position is too large (ie, writing at Int64.MaxValue 
    // on Win9x) OR for synchronous writes to a handle opened 
    // asynchronously.
    if (hr == ERROR_INVALID_PARAMETER)
        throw new IOException(Environment.GetResourceString("IO.IO_FileTooLongOrHandleNotSync"));
    __Error.WinIOError(hr, String.Empty);
}

The above code was taken from FileStream.cs , the method is Write.

There are two cases where an IOException will be thrown during Dispose/Close. One will be using a position that is greater than Int64.maxValue on a Win9x system. The second is trying to write synchronously to a handle that was opened asynchronously.

I really doubt that you're using a Win9x system so that really isn't a consideration. The second one is a little more likely to crop up, although it is very unlikely from what I can tell and should be caught in development.

I would say you are fine using a "using" statement in this case. The IOException is an edge that is unlikely to pop up and if it does it will likely be during development.

Unless of course you're developing on a Windows 98 machine, in that case you should just quit.

Side note: This answer is based on my interpretation of the code in FileStream.cs. If I made any incorrect assumptions, please let me know and I'll adjust my answer appropriately.