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I a have a Checkbox on my form witch checked property is bound to a single object's boolean property. The update mode is set to OnPropertychanged cause there's no need for validation and i don't want the user having to click else where or press tab to commit that kind of change.

The problem is that the BindingSource calls the object's property setter a second time right after the checkbox looses focus just as if the update mode was OnValidation! That cause a terrible mess in my application...

The object implements the INotifyPropertyChanged but i removed the call to my helper method that raise the PropertyChanged event to see if that was the cause of that double call and it's not.

I just don't get it! why that behavior?
Posted 8-Nov-13 9:19am
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It is called twice because you programmed it this way, nothing else. How can we know what have you done? Use the debugger.
—SA
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Solution 1

Please see my comment to the question.

Such problems are easily resolved using the debugger with one of its wonderful tools: "Call Stack" window. If you use Visual Studio, use [main menu] Debug => Windows => Call Stack, and a breakpoint at the property setter. The stack will show you where the call comes at first place and other cases.

—SA
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Solution 2

I always make extensive use of all debugging features and logic to track problems like these, the call stack does not help unless i turn "just my code" off and dive into that stuff the debug output shows me. It sometimes help find errors in my own code but not always.

I solved this issue with that stupid kind of workaround i hate; by modifying my property setter in a way to ignore the unwanted call by comparing "value" with the Private Field of the class's property and it work like a expected.

I Just can't imagine working without Data Bindings but i frequently have to face situations like this with the bindingsource component.
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