A strange question

[seabluescn]

Model:

public class Tester
{
    public float Tester_PA { get; set; }
}

ViewModel:

public Tester Tester { get; set; }
public void DoTest()
{
    Tester = new Tester
    {
        Tester_PA = 1.2f
    };
    Tester.Tester_PA = 2.3f;
}

View:

<TextBlock Text="{Binding Path=Tester.Tester_PA }" />

Why does it show 1.2 instead of 2.3?

[canton7]

More details please. Cam you post the full classes, not just snippets? How and when is DoTest called?

[seabluescn]

That's all the code.

WpfApp10.zip

[canton7]

Right, you're using PropertyChanged.Fody to insert INotifyPropertyChanged events.

PropertyChanged.Fody works on classes which implement INotifyPropertyChanged, and it rewrites properties to automatically raise the PropertyChanged event whenever the property is assigned.

Your MainViewModel implements INotifyPropertyChanged (it inherits from Screen, which implements that interface). So, PropertyChanged.Fody gets to work and rewrites the Tester property so that when you assign to it, it raises the PropertyChanged event.

The Binding in your view then listens for that event, and refreshes itself when it's raised. So when you assign to Tester, the view gets a notification that the property has changed.

Your Tester model does not implement INotifyPropertyChanged, and so PropertyChanged.Fody does not rewrite any of its properties to raise the PropertyChanged event. So when you assign to Tester.Tester_PA, no event is raised, and the view does not know that anything has been changed.

[seabluescn]

I see. Thank you!

[seabluescn]

public class Tester: INotifyPropertyChanged
{
public float Tester_PA { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
}

That's working fine.