INotifyPropertyChanged
Provide a way for INotifyPropertyChanged to be implemented for you automatically on class.
Provide a way for INPC to be done on auto properties (that you mark in some way)....so that you don't have to unroll the auto property into a field, and raise yourself.
jams
shared this idea
13 comments
-
Ramon de Klein commented
Implementing INotifyPropertyChanged properly requires some repeating programming effort for each property. It also used to be error-prone, but this can be resolved in C# 5 using the CallerMemberName attribute. It would be more convenient to use automatic properties with INotifyPropertyChanged support. The 'SupportINotifyPropertyChanged' attribute can be applied to automatic properties and this result in the following code:
[SupportINotifyPropertyChanged]
public string Description { get; set; }Is compiled to something like this:
private string __description;
public Description
{
get { return __description; }
set {
if (__description == value) return;
__description = value;
var propChanged = (INotifyPropertyChanged)this; /* prevents race condition */
if (propChanged != null)
propChanged(this, new PropertyChangedEventArgs("Description"));
}
}A compilation error will be emitted if the class (or one of its parents) doesn't implement the INotifyPropertyChanged interface.
As an addition the 'SupportINotifyPropertyChanged' attribute could also take an optional Func<T,T,bool> delegate (or use IEqualityComparer<T>) that is used to check if the new value is different for more complex scenarios.
-
Implementing INotifyPropertyChanged properly requires some repeating programming effort for each property. It also used to be error-prone, but this can be resolved in C# 5 using the CallerMemberName attribute. It would be more convenient to use automatic properties with INotifyPropertyChanged support. The 'SupportINotifyPropertyChanged' attribute can be applied to automatic properties and this result in the following code:
[SupportINotifyPropertyChanged]
public string Description { get; set; }Is compiled to something like this:
private string __description;
public Description
{
get { return __description; }
set {
if (__description == value) return;
__description = value;
var propChanged = (INotifyPropertyChanged)this; /* prevents race condition */
if (propChanged != null)
propChanged(this, new PropertyChangedEventArgs("Description"));
}
}A compilation error will be emitted if the class (or one of its parents) doesn't implement the INotifyPropertyChanged interface.
As an addition the 'SupportINotifyPropertyChanged' attribute could also take an optional Func<T,T,bool> delegate (or use IEqualityComparer<T>) that is used to check if the new value is different for more complex scenarios.
-
Brett
commented
This is improved in VS11 net4.5 to use the method name optionally as [CallerMemberName] string PropertyName where the callername is subsitituted if no explicit name is supplied
-
Miha Markic
commented
Agree with Schuster-Rainer - AOP is the way to go. Roslyn might have this feature albeit I doubt it (due to the political decisions). As for now, there are AOP 3rd parties ranging from free ones (as RIchard pointed out) to much more powerful (not free, but well worthi it) PostSharp.
The bottom line is that if MS is to add this feature it will be a part of Roslyn. And yes, I am totally in favor of such a feature. -
apr
commented
This idea won't work for a winform/wpf(?) application, when the property is changed in a non-ui thread.
-
Richard Collette
commented
NotifyPropertyWeaver already provides this type of functionality.
http://code.google.com/p/notifypropertyweaver/The plus of it being in the platform would be long term support. The plus of it being outside the platform as it is now is that we get a much more frequent update cycle.
-
Qwertie
commented
I would only support this idea as part of a far more general metaprogramming feature. I imagine writing an auto-property like [FirePropertyChanged] int Foo {get;set;}, and then a compile-time FirePropertyChangedMetaAttribute(...) method would transform that into a property that fires PropertyChanged when called.
-
Schuster-Rainer
commented
Implement serverall compiler stages, or some kind of macros / AST transformation, or simply AOP, so this will be no problem anymore.
-
Alan Rotenberg
commented
Tangential to this but very related, it's kind of annoying to always have to test if an event is null before raising it. It's pretty tedious to always have to test of PropertyChanged is null. It should just do nothing if there are no subscribers.
-
Tuomas Hietanen commented
It would be nice to have it like attribute to class, like [NotifyPropertyChange]
However, events are actually just side effects (hard to test etc.), so I think that the whole event-driven software development model is bad. It seems to be the default model. :-(
-
Daver
commented
Most of the time, creating this INotifyPropertyChanged code is just mindless grunt work. It would be nice if it was assumed by convention to work a starndard way. And if you need it to behave non-standard, then allow it to be overridden somehow.
-
Daver
commented
Most of the time, creating this INotifyPropertyChanged code is just grunt work. It would be nice if it was assumed by convention to work a starndard way. And if you need it to behave non-standard, then allow it to be overridden somehow.
-
Anonymous
commented
Also add Raise feature like in VB and auto-event support with thread-safe raise implementation
public event EventHandler ChangingEvent { add; remove; raise; }
