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Aug 13, 2008
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The implementation of iterators in C# and its consequences (part 2)

Raymond Chen

Now that you have the basic idea behind iterators under your belt, you can already answer some questions on iterator usage. Here's a scenario based on actual events: I have an iterator that is rather long and complicated, so I'd like to refactor it. For illustrative purposes, let's say that the enumerator counts from 1 to 100 twice. (In real l...

Code
Aug 12, 2008
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The implementation of iterators in C# and its consequences (part 1)

Raymond Chen

Like anonymous methods, iterators in C# are very complex syntactic sugar. You could do it all yourself (after all, you did have to do it all yourself in earlier versions of C#), but the compiler transformation makes for much greater convenience. The idea behind iterators is that they take a function with yield return statements (and possible s...

Code
Aug 11, 2008
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Psychic debugging: Why can’t StreamReader read apostrophes from a text file?

Raymond Chen

As is customary, the first day of CLR Week is a warm-up. Actually, today's question is a BCL question, not a CLR question, but only the nitpickers will bother to notice. Can somebody explain why StreamReader can’t read apostrophes? I have a text file, and I read from it the way you would expect: StreamReader sr = new StreamReader("myfil...

Code
Aug 8, 2008
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If you return FALSE from DLL_PROCESS_ATTACH, will you get a DLL_PROCESS_DETACH?

Raymond Chen

If you return from , will you get a ? Yes. No. ... Yes. All three answers are correct, for different formulations of the question. From the kernel's point of view, the answer is a simple Yes. If a DLL's entry point returns to the notification, it will receive a notification. However, most C and C++ programs do not use the ra...

Code
Aug 6, 2008
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The caret serves as the continuation character for batch files

Raymond Chen

We saw earlier that the caret is the escape character for the batch language. In a comment to that article, KJK::Hyperion mentioned that the caret serves as the line continuation character. A useful tip if you still find yourself messing with batch files. Mark Yocum elaborates on this point a bit more.

Code
Aug 1, 2008
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I warned you: The dangers of attaching input queues

Raymond Chen

Some people didn't take to heart my cautions on the subject of attached input queues, item number five on the list of five things every Win32 programmer should know. And then they find that their application stops responding. // Code in italics is wrong void TryToStealFocus(HWND hwnd) { // First try plain SetForegroundWindow SetForegroundWi...

Code
Jul 25, 2008
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Simulating a drop, part two

Raymond Chen

Last time, we wrote a tiny program to simulate dropping a file on another file, but we discovered that it didn't work for dropping a file onto Mail Recipient.MAPIMail. The reason, as you no doubt instantly recognized, is that the MAPIMail handler creates a worker thread, and we're exiting the process before the worker thread has finished its work....

Code
Jul 24, 2008
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Reading a contract from the other side: Simulating a drop

Raymond Chen

Most people, when they think of the IDropTarget interface, think only of implementing a drop target. But you can read the contract from the other side, because the description of how a drag source interacts with a drop target tells you how to be a drag source. To summarize, the sequence of drop target operations go like this: IDropTarget::Drag...

Code
Jul 23, 2008
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Theorize if you want, but if the problem is right there in front of you, why not go for the facts?

Raymond Chen

On an internal discussion list, somebody asked a question similar to this: My program launches a helper program. This helper program does different things based on the command line parameters, but the way I'm using it, it just prints its results to the console and exits. When I launch this program and wait for it to exit, my wait never completes....

Code