WPF: Save on window close

Here are a few thoughts

1.       You can have your inherited controls expose data provider instead having BOSave.  You can probably even skip that if you follow a naming convention for provider name, although this seems dirty to me.

2.       At that point you can

a.       Check for changes

b.      Set provider to be synchronous, as I do not think asynchronous mode will work here.

c.       Add event handler for data changed

d.      Fire Save() on provider

e.      Data Changed I think will fire two times (to force UI refresh)

f.        If error is not null in first Data Changed handler, you know you have the error.

g.       After second Data Changed you can remove handler.

h.      Reset provider back to original state (synch or async)

i.         Check for error

j.        If there was one, popup the message, set cancel to true.

k.       Else close the form

Sergey Barskiy

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Hi,

I'm trying to build up my Wpf library of general helper classes to give a consistent user experience.

I'm creating a user control which contains everything needed to edit a business object.  I'm also creating a BusinessEditWindow, which is a subclass of Wpf's Window.

I'm trying to override the OnClosing method.  The goal is to prompt the user if the window is closing at the BO is dirty.  If the BO isn't valid, the choice is close the window and lose changes, or cancel closing of the window.

If the object is valid though, there are three choices.  Saving the BO and closing the window, discarding the BO and closing the window, or canceling the window close.

The problem is with the save; if there's an error, I want to throw up my error dialog, and cancel the window closing.  I'm hitting a problem though, and I'm not sure how to solve it.

My initial idea was to have every control implement a SaveBusinessObject method, which returns true or false; true means the BO saved, false means there was some kind of exception.  Not sure how to code that, since the CslaDataProvider is handling the save command for me.

My next choice was to allow an exception to be thrown.. except the DataProvider's model is to check the Error property of the DP I'm guessing in an event handler for DataChanged.  the problem there is throwing and catching the exception doesn't allow the CslaDataProvider to reset the BO to the instance prior to calling save.

So, I'm not sure how I should continue here.  I also have concerns because the DataProvider is asyncronous, so that my UI stays nice and snappy and windows open immediately.

Thanks
Andy