Don't Forget to Flush!

I saw something new today that I haven't seen since my C++ days:  a stream that needed to be flushed. 

I have to admit, this one boggled me for about 15 minutes before I realized what was going on.  Then I caught a mistake I haven't made in years:  I forgot to close an open StreamWriter.

The function is a simple one.  It iterates through decorated methods in my Program.cs file, finds the command name through reflection (thanks to a colleague of mine), and streams the command name to a text file for later review (after some collection manipulation and sorting).  Here was the original method:



As you can see, it looks pretty innocent.  Except for one small problem:  In a collection of 60 strings, only 44 1/2 of the strings were being streamed!  Yes, you saw that correctly.  Only 44.5 of the 60 total strings were being written to the text file.  Then I had a C++ flashback that threw me into a post traumatic stress episode...

Back in C++ we had to routinely "flush" our streams to make sure all the data made it safely to its destination.  I don't ever recall having to explicitly flush ANYTHING in C# or, dare I say it, VB.Net (<gasp>)!  Then I looked back at my code and slapped myself square on the face.

I forgot to close the stupid stream :(   15 minutes down the toilet because I forgot to flush (pun intended).  In C#, making a call to StreamWriter.Close() causes an implicit flush to take place.  No, I don't know or understand the details yet.  I just know it happens.

With a single line of code:  sw.Close();  I was able to successfully stream all of my commands to the text file.  Here is the finished product:



Not much of a difference in implementation, huh?  But a HUGE difference in effect.