Example of DependencyProperty #wpf #csharp

attachedPropertyExample.cs

public static readonly DependencyProperty TopProperty =
    DependencyProperty.RegisterAttached("Top", 
    typeof(double), typeof(Canvas),
    new FrameworkPropertyMetadata(0d,
        FrameworkPropertyMetadataOptions.Inherits));
 
public static void SetTop(UIElement element, double value)
{
    element.SetValue(TopProperty, value);
}
 
public static double GetTop(UIElement element)
{
    return (double)element.GetValue(TopProperty);
}

attachedPropertyExample.xaml

<!-- To set the value of an attached property, add an attribute in XAML with a prefix of the element that 
provides the attached property. To set the the Canvas.Top and Canvas.Left property of a button aligned within 
a Canvas panel, you write it like this: -->
<Canvas>
    <Button Canvas.Top="20" Canvas.Left="20" Content="Click me!"/>
</Canvas>

DependencyPropertyExample.cs

public class DependencyPropertyExample
{
	// Dependency Property
	public static readonly DependencyProperty CurrentTimeProperty = 
			DependencyProperty.Register( "CurrentTime", typeof(DateTime),
			typeof(MyClockControl), 
			new FrameworkPropertyMetadata( DateTime.Now, 
				 OnCurrentTimePropertyChanged, // optional
				 OnCoerceCurrentTimeProperty ), // optional
				 OnValidateCurrentTimeProperty );  // optional

	// .NET Property wrapper
	public DateTime CurrentTime
	{
		get { return (DateTime)GetValue(CurrentTimeProperty); }
		set { SetValue(CurrentTimeProperty, value); }
	}

	private static void OnCurrentTimePropertyChanged(DependencyObject source, DependencyPropertyChangedEventArgs e)
	{
		MyClockControl control = source as MyClockControl;
		DateTime time = (DateTime)e.NewValue;
		// Put some update logic here...
	}

	private static object OnCoerceTimeProperty( DependencyObject sender, object data )
	{
		if ((DateTime)data > DateTime.Now )
		{
			data = DateTime.Now;
		}
		return data;
	}
	
	private static bool OnValidateTimeProperty(object data)
	{
		return data is DateTime;
	}
}

DependencyPropertyListenerExample.cs

DependencyPropertyDescriptor textDescr = DependencyPropertyDescriptor.
    FromProperty(TextBox.TextProperty, typeof(TextBox));
 
if (textDescr!= null)
{
    textDescr.AddValueChanged(myTextBox, delegate
    {
        // Add your propery changed logic here...
    });
} 

readOnlyDependencyPropertyExample.cs

// used to report the state of a control, like the IsMouseOver property. Is does not make sense to provide a setter for this value.

// Register the private key to set the value
private static readonly DependencyPropertyKey IsMouseOverPropertyKey = 
      DependencyProperty.RegisterReadOnly("IsMouseOver", 
      typeof(bool), typeof(MyClass), 
      new FrameworkPropertyMetadata(false));
 
// Register the public property to get the value
public static readonly DependencyProperty IsMouseoverProperty = IsMouseOverPropertyKey.DependencyProperty;    
 
// .NET Property wrapper
public int IsMouseOver
{
   get { return (bool)GetValue(IsMouseoverProperty); }
   private set { SetValue(IsMouseOverPropertyKey, value); }
}