I have an bitmap and an property like this :
private Bitmap host_Bitmap; private Bitmap Host_Bitmap {get;set;} How can I create an event when the host_Bitmap change?
- Also MSDoc articles: How to: Implement Property Change Notification and INotifyPropertyChanged.PropertyChanged Événementuser12031933– user120319332021-01-04 07:05:35 +00:00Commented Jan 4, 2021 at 7:05
- Also using simple events: Data binding without INotifyPropertyChangeduser12031933– user120319332021-01-04 07:08:36 +00:00Commented Jan 4, 2021 at 7:08
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1 Answer
If you want to take the simple route for one property, you add an event, and in the set you invoke it:
public event EventHandler BitmapChanged; private Bitmap _hostBitmap; public Bitmap HostBitmap { get => _hostBitmap; set{ _hostBitmap = value; BitmapChanged?.Invoke(this, EventArgs.Empty); } } If you want to pass more info about the event you can provide a modified EventArgs subclass and declare the BitmapChanged property type to be EventHandler<YourEventArgsSubclass>
If you have a lot of properties to associate with events, look at implementing INotifyPropertyChanged
15 Comments
Also instead of using
EventHandler<> a delegate can be created to be used for the type of the event, thus it will be strongly typed.
Peter Duniho
@OlivierRogier: while I don't find this answer to be of much use (there are plenty of duplicates already on the site), I don't understand your critique here. The
EventHandler and EventHandler<T> types are both already delegate types. Using either creates just as "strongly typed" an event as using any other delegate type would.
Caius Jard
@Olivier Yes, but that is probably only necessary in exceptional circumstances such as when in a context that doesn't understand the generic
EventHandler<T> - the documentation outlines that it shouldn't really be necessary to do it so I'm not sure that saying "instead of" is "right", because (to me) it implies a circumstance that is commonly necessary, when it isn't necessary?What I meant by strongly typed on top of a generic is not a critic but just an alternative meaning that it can sometimes be easier and cleaner to use a dedicated type like for example a
MyPropertyChanged delegate instead of a circumstantial Eventhandler<MyArgs>. Otherwise I find the answer adapted and personalized.Chinh Cross
Thank you for helping, I will try it out
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