Is it possible to Edit and Continue in Visual Studio 2010 without pausing execution?

Question

I recently watched a bit of Notch's Ludum Dare live stream. He uses Eclipse's hotswap feature extensively while he works on his game. (here is a video of what I am referring to http://www.twitch.tv/notch/b/302823358?t=86m30s)

I would like to do the same with C# and XNA. Fortunately, Visual Studio has an Edit and Continue feature. However, I would like to edit my rendering code while it is running instead of pausing it.

Is it possible for me to setup Visual Studio to do the same? I noticed that there is a checkbox for Break all processes when one process breaks. Is it maybe possible to set up my rendering loop in another thread so that the game keeps rendering while I make a change?

Answer 1

Update: This answer is now available as a video.

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I've been struggling to find a way to do this. I know this doesn't answer your exact question. But really what you are looking for is a workflow where you can make code changes with zero (or near-zero) delay, and I think I've figured out the closest you can get with just Visual Studio. (And therefore avoiding a huge engineering effort and dealing with "abnormal" projects).

The way to achieve this workflow is actually astonishingly simple, once you think of it:

Use shortcut keys!

The first way I came up with is to just use the normal edit-and-continue method of setting a breakpoint. Only by using the keyboard you can do this considerably faster. This only works with code being called in a loop (eg: draw/update). Click the code you want to modify, add a breakpoint (F9), the breakpoint will almost immediately be hit, modify your code, remove the breakoint (F9), and then run the code again (F5).

This is pretty good. You don't have to use the mouse to hit the relatively small "Add breakpoint" target in the left hand column. But it does move the input focus to the beginning of the line, so you generally have to use the mouse again to fix that before you can start editing.

I want something faster. So I came up with a better solution:

Again, using the keyboard: Press Ctrl + Alt + Break to "Break All". This enters the debugger almost instantly, without having to worry about setting a breakpoint or if the code you want to modify is running in a loop. This will change the editor window and caret focus to the document where execution break, but you can then immediately fix it by pressing Ctrl + - for "Navigate Backwards".

Then you can make your edits and simply press F5 to see them in action. You only have to use the mouse once (or not at all) to initially pick where you want to start typing - just as you would expect.

Admittedly Ctrl + Alt + Break and Ctrl + - are horrible key combinations for something you want to be able to do extremely quickly. And it would be better if there was just one key to press.

If you have the full Visual Studio, you could probably turn it into a macro or add-in. Express doesn't have those - so the best you can do is modify your key bindings (Tools, Customise, Keyboard...) and bind it to two keys that are adjacent, that you can press in quick succession. Or use an external macro utility.

Personally I have set up the two key combinations to be pressed in succession (you don't seem to need a delay between the two) by a macro set to a spare button on my mouse. Which works reasonably well - as I'm usually selecting text at the same time. I might add a keyboard macro later too.

So far I've identified two minor pitfalls of this method:

• When you run the app again, Visual Studio gives it focus. It would be nice if it kept focus. Adding a left mouse click to my macro is a partial solution to quickly re-editing code.
• "Navigate Backwards" does not retain the text selection, only the caret position.