WPF dependency property Databinding

Question

I have very basic question regarding dependency property and data-binding. I have created a simple class name TDTVm its my ViewModel class. It has one bool dependency property named IsShaftMovingUp and its initial value is 'False' I have bound this value to one text box on UI. Now I want to show real-time value of 'IsShaftMovingUp' on the screen.

Below is my VM.

public class TDTVm : DependencyObject
{
    public static DependencyProperty ShaftMovingUpProperty = 
        DependencyProperty.Register(
            "ShaftMovingUp", 
            typeof(bool),
            typeof(TDTVm),
            new PropertyMetadata(false, ShaftMovingUpChanged));

    private static void ShaftMovingUpChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        Console.WriteLine("ok");
    }

    public bool IsShaftMovingUp 
    {
        get => (bool)GetValue(TDTVm.ShaftMovingUpProperty);                
        set => SetValue(TDTVm.ShaftMovingUpProperty, value);
    }
}

Below is my xamal code.

        <Window x:Class="WpfApplication1.MainWindow"
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">    
        <Grid>      
            <Button Content="Button" Click="Button_Click"/>
            <TextBox Text="{Binding IsShaftMovingUp,
                     UpdateSourceTrigger=PropertyChanged}" />
        </Grid>
    </Window>

and below is my code behind:

public partial class MainWindow : Window
{
    TDTVm datacontext = new TDTVm();

    public MainWindow()
    {
        InitializeComponent();
        this.DataContext = datacontext;
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        ///Even after this line 'true' value is not getting updated on UI.
        datacontext.IsShaftMovingUp = true;
    }
}

When I click on button I am setting value of 'IsShaftMovingUp' to true. But still on UI its not getting updated. ( I have achieved this using INotifyPropertyChanged but want to try same with dependency property to understand exact difference between the two )

Thanks

score 2 · Accepted Answer · edited May 23 '17 at 12:07

2

To fix your problem, you need to change this code

DependencyProperty.Register("ShaftMovingUp",

into

DependencyProperty.Register("IsShaftMovingUp",

Check this post, if you want to know the difference between INotifyPropertyChanged and Dependency Property.

edited May 23 '17 at 12:07

Community

1
1

answered Jul 19 '14 at 04:06

Yuliam Chandra

14,494
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That's exactly the reason to avoid those strings and go with ```DependencyProperty.Register(nameof(IsShaftMovingUp),``` instead. nameof() will give you compile errors immediatelly. – ecth Feb 16 '21 at 09:21

WPF dependency property Databinding

1 Answers1