Implementing INotifyPropertyChanged - does a better way exist?

user_149190 0
Viewed 361071

Microsoft should have implemented something snappy for INotifyPropertyChanged, like in the automatic properties, just specify {get; set; notify;} I think it makes a lot of sense to do it. Or are there any complications to do it?

Can we ourselves implement something like 'notify' in our properties. Is there a graceful solution for implementing INotifyPropertyChanged in your class or the only way to do it is by raising the PropertyChanged event in each property.

If not can we write something to auto-generate the piece of code to raise PropertyChanged event?

inotifypropertychanged winforms .net c#
35 Answers

Whilst there are obviously lots of ways to do this, with the exception of the AOP magic answers, none of the answers seem to look at setting a Model's property directly from the view model without having a local field to reference.

The issue is you can't reference a property. However, you can use an Action to set that property.

protected bool TrySetProperty<T>(Action<T> property, T newValue, T oldValue, [CallerMemberName] string propertyName = null)
{
    if (EqualityComparer<T>.Default.Equals(oldValue, newValue))
    {
        return false;
    }

    property(newValue);
    RaisePropertyChanged(propertyName);
    return true;
}

This can be used like the following code extract.

public int Prop {
    get => model.Prop;
    set => TrySetProperty(x => model.Prop = x, value, model.Prop);
}

Check out this BitBucket repo for a full implementation of the method and a few different ways of achieving the same result, including a method that uses LINQ and a method that uses reflection. Do note that these methods are slower performance wise.

user_46011490

I'm writing a library that deals with INotifyPropertyChanged, and the main idea is using a dynamic proxy to notify changes.

the repo is here: CaulyKan/NoMorePropertyChanged

with this library, you can write:

    public dynamic Test1Binding { get; set; }
    public TestDTO Test1
    {
        get { return (TestDTO)Test1Binding; }
        set { SetBinding(nameof(Test1Binding), value); }
    }

Then make all bindings and modifications go to Test1Binding, which will notify PropertyChange and CollectionChanged automatically no matter how complex TestDTO is.

it can also handle dependencies.

    [DependsOn("Test1Binding.TestString")]
    public string Test2
    {
        get { return Test1Binding.TestString; }
    }

Please give me some suggestions.

user_3766980

It's 2022. Now there's an official solution.

Use the MVVM source generators in Microsoft MVVM Toolkit.

This

[ObservableProperty]
private string? name;

will generate:

private string? name;

public string? Name
{
    get => name;
    set
    {
        if (!EqualityComparer<string?>.Default.Equals(name, value))
        {
            OnNameChanging(value);
            OnPropertyChanging();
            name = value;
            OnNameChanged(value);
            OnPropertyChanged();
        }
    }
}

// Property changing / changed listener
partial void OnNameChanging(string? value);
partial void OnNameChanged(string? value);

protected void OnPropertyChanging([CallerMemberName] string? propertyName = null)
{
    PropertyChanging?.Invoke(this, new PropertyChangingEventArgs(propertyName));
}

protected void OnPropertyChanged([CallerMemberName] string? propertyName = null)
{
    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

It supports .NET standard 2.0 and .NET >= 5.0.

user_95113050
Related