Doesnt like NotifyPropertyChanged(() => IsChecked);

Question

The lines where I have NotifyPropertyChanged(()=IsChecked) I get a compiler error that says the name NotifyPropertyChanged does not exist in the current context. Also, I was wondering are those methods NotifyPorpertyChanged Delegates that point to the anonymous lambda expression () => IsChecked? Also below I am having issues with my VIEW giving me compiler errors. line local:KeypadViewModel the compiler error says The type 'local:KeypadViewModel was not found. Verify that you are not missing an assembly reference and that all referenced assemblies have been built. And on the EntryText line it says The property content is set more than once.

public class MyViewModel : INotifyPropertyChanged

{

const string Msg1 = "blah 1";

const string Msg2 = "blah 2";

private bool _isChecked;

public bool IsChecked

{

    get { return _isChecked; }

    set

    {

        if (_isChecked == value) return;

        _isChecked = value;

        MyBoundMessage = _isChecked ? Msg1 : Msg2;

        //NotifyPropertyChanged(() => IsChecked);

        //NotifyPropertyChanged(() => MyBoundMessage);

    }

}

public string MyBoundMessage { get; set; }

public event PropertyChangedEventHandler PropertyChanged;

protected virtual void OnPropertyChanged(string propertyName)

{

    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

}

}

<?xml version="1.0" encoding="utf-8" ?> <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"              xmlns:local="clr-namespace:MauiApp3"              
x:Class="MauiApp3.MainPage"              
Title="Keypad Page">     
<ContentPage.BindingContext>         
<local:KeypadViewModel/>     
</ContentPage.BindingContext>     
<CheckBox IsChecked="{Binding IsChecked}" />     
<Entry Text="{Binding MyBoundMessage}" />  
</ContentPage>

Answer 1

Instead of NotifyPropertyChanged, try this: OnPropertyChanged("IsChecked"); OnPropertyChanged("MyBoundMessage"). The latter can be moved to the setter of MyBoundMessage.

You can also write OnPropertyChanged(nameof(IsChecked)).

The lambda expressions are not used in this approach.

Also try <local:MyViewModel/>.