Could not change the property value dynamically in button click - xamarin.forms

Question

I have created bindable property called Text in TargetClass.cs. That Text property is nested bindable property.
TargetClass.cs :
public class TargetClass : BindableObject
{
public static readonly BindableProperty TextProperty =
BindableProperty.Create("Text", typeof(string), typeof(TargetClass), "Default", BindingMode.TwoWay, null,
OnTextChanged);
private static void OnTextChanged(BindableObject bindable, object oldValue, object newValue)
{
}
public string Text
{
get
{
return (string)GetValue(TextProperty);
}
set
{
SetValue(TextProperty, value);
}
}
}
ViewModel.cs :
public class ViewModel : INotifyPropertyChanged
{
private string m_text = "New Value";
public string TextValue
{
get { return m_text; }
set
{
m_text = value;
OnPropertyChanged("TextValue");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
Then I have created MyView.cs
public class MyView : ContentView
{
private TargetClass target;
Label label;
public TargetClass Target
{
get
{
return target;
}
set
{
target = value;
label.Text = target.Text;
}
}
public MyView()
{
label = new Label();
label.FontSize = 50;
Content = label;
}
}
MainPage.xaml :
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
xmlns:local="clr-namespace:BindingDemo"
x:Class="BindingDemo.MainPage">
<StackLayout>
<local:MyView >
<local:MyView.Target>
<local:TargetClass Text="{Binding TextValue}" >
<local:TargetClass.BindingContext>
<local:ViewModel />
</local:TargetClass.BindingContext>
</local:TargetClass>
</local:MyView.Target>
</local:MyView>
<Button Text="Click" Clicked="Button_Clicked" />
</StackLayout>
MainPage.xaml.cs:
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
}
private void Button_Clicked(object sender, EventArgs e)
{
(BindingContext as ViewModel).TextValue = "Latest Value";
}
}
TextValue property is binded with Text bindble property.
I have changed value of TextValue property in button click in MainPage.xaml.cs.
If I click the button. it should show Latest value. But it shows new value,it did not changed from new value to latest value.
Is it possible to change the value of TextValue property in Button click dynamically ?

Answer 1

If you want to use the method above,you could check below (But it's not recommended.If TargetClass is not used anywhere else, this class seems redundant, you can add a BindableProperty to MyView directly):
in TargetClass.cs:
public class TargetClass : BindableObject
{
public static readonly BindableProperty TextProperty =
BindableProperty.Create("Text", typeof(string), typeof(TargetClass), "Default", BindingMode.TwoWay, propertyChanged: OnTextChanged);
private static void OnTextChanged(BindableObject bindable, object oldValue, object newValue)
{
((TargetClass)bindable).View.label.Text = (string)newValue;
}
public string Text
{
get
{
return (string)GetValue(TextProperty);
}
set
{
SetValue(TextProperty, value);
}
}
public static readonly BindableProperty ViewProperty =
BindableProperty.Create("View", typeof(MyView), typeof(TargetClass), null, BindingMode.TwoWay);
public MyView View
{
get
{
return (MyView)GetValue(ViewProperty);
}
set
{
SetValue(ViewProperty, value);
}
}
}
in the page.xaml:
<StackLayout >
<local:MyView x:Name="MyView">
<local:MyView.Target>
<local:TargetClass x:Name="MyClass" View="{Binding ., Source={x:Reference MyView}}" Text="{Binding TextValue}" >
<local:TargetClass.BindingContext>
<local:ViewModel />
</local:TargetClass.BindingContext>
</local:TargetClass>
</local:MyView.Target>
</local:MyView>
<Button Text="Click" Clicked="Button_Clicked" />
</StackLayout>
in page.xaml.cs:
private void Button_Clicked(object sender, EventArgs e)
{
(MyClass.BindingContext as ViewModel).TextValue = "Latest Value";
}