Question

I have a DependencyObject class

public class TestDependency : DependencyObject
{
    public static readonly DependencyProperty TestDateTimeProperty ...

    public DateTime TestDateTime {get... set..}
}

my window is like this

public partial class MainWindow : Window{

    public TestDependency td;
    public MainWindow()
    {
        InitializeComponent();
        td = new TestDependency();
        td.TestDateTime = DateTime.Now;
    }
}

If I wanna bind the TestDateTime property of MainWindow’s dependency object td (public TestDependency td;) to a textbox in Xaml, how do I bind it? This is what I am doing now

<TextBlock Name="tb" Text="{Binding Source = td, Path=TestDateTime, TargetNullValue=novalue}"/>

It doesn’t work at all. Anyone knows what I need to change?

Answer 1

First, you’ll need to define td as a property rather than a field, since you can only bind to properties:

public TestDependency td { get; private set; }

Then, make sure you set the data context in your window’s constructor:

public MainWindow()
{
    td = new TestDependency();
    td.TestDateTime = DateTime.Now;
    this.DataContext = this;

    InitializeComponent();
}

Lastly, set the binding in XAML:

<TextBlock Name="tb" Text="{Binding Path=td.TestDateTime}" />