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Binding WPF with a DataContext with a class and subclass

I am playing with databinding in wpf and I ran into a problem. Here is my code:

MainWindow.xaml

<Window x:Class="TestWpf.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:TestWpf"
        Title="MainWindow" Height="350" Width="525">    
    <StackPanel Name="stackpanel">
        <TextBox Name="tb1" Text="{Binding Path=A.Number}" />
        <TextBox Name="tb2" Text="{Binding Path=B.Number}" />
        <TextBlock Name="tbResult" Text="{Binding Path=C}" />
    </StackPanel>
</Window>

MainWindow.xaml.cs

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        MyClass myClass = new MyClass();
        myClass.A = new MySubClass();
        myClass.B = new MySubClass();
        stackpanel.DataContext = myClass;
    }
}

Myclass.cs

class MyClass : INotifyPropertyChanged
{
    private MySubClass a;
    public MySubClass A 
    {
        get { return a; }
        set
        {
            a = value;
            OnPropertyChanged("A");
            OnPropertyChanged("C");
        }
    }

    private MySubClass b;
    public MySubClass B 
    {
        get { return b; }
        set
        {
            b = value;
            OnPropertyChanged("B");
            OnPropertyChanged("C");
        }
    }

    public int C
    {
        get { return A.Number + B.Number; }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged(string p)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(p));
        }
    }        
}

MySubClass.cs

class MySubClass : INotifyPropertyChanged
{
    private int number;
    public int Number 
    {
        get { return number; }
        set
        {
            number = value;
            OnPropertyChanged("Number");
        }
    }

    public MySubClass()
    {
        Number = 1;
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged(string p)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(p));
        }
    }     
}

Now the problem is that the binding works fine after starting the application. Also, the A.Number and B.Number values ​​are updated normally when I change them in the text box. But the C variable in MyClass.C is updated only when the application starts and never appears. What do I need to change to update C when A.Number or B.Number changes. Thank.

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2 answers

When updating a data model, do you change the number directly on MySubClass instances or do you assign new subclasses to the MyClass instance? i.e:

myClass.A.Number = 5; // will trigger OnPropertyChanged on MySubClass, but not on MyClass

OnPropertyChanged A (, , A.Number). - :

MySubClass v = new MySubClass()
v.Number = 5;
myClass.A = v;  // will trigger OnPropertyChanged on MyClass

. , b.

public MyClass()
{
    a.PropertyChanged += new PropertyChangedEventHandler(UpdateC);
    b.PropertyChanged += new PropertyChangedEventHandler(UpdateC);
}

void UpdateC(object sender, PropertyChangedEventArgs e)
{
    OnPropertyChanged("C");
}
+3
, C A.Number B.Number.

A B. , :



set
{
if (a != null)
{
 a.PropertyChanged-=NumberChanged;
}
 a = value;
 a.PropertyChanged+=NumberChanged;
 OnPropertyChanged("A");
 OnPropertyChanged("C");
}

private void NumberChanged(object sender, PropertyChangedEventArgs e)
{
  if (e.PropertyName == "Number")
  {
    OnPropertyChanged("C");
  }
}

B.

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