Using this approach, you can now save the desired security ID into the table of values the Dependency Property system keeps. In this example, I chose to call that namespace “my.” In order to reference the new class, you must declare an XML namespace to point to the. (For this to work, the object must inherit from DependencyObject in some form, as every UI element does.)Īs a result, you can now use the new object in XAML like this: This is what makes the property look like a normal property to the users of this system. NET property, which uses the GetValue() and SetValue() methods to store and retrieve the values from the Dependency Property system. The property itself is defined as a static, read-only member of the class, which registers itself with the Dependency Property system by providing details such as the name, the type, the class the property goes with, and the default value (as well as other optional parameters). Note that there are two parts to the definition of a Dependency Property. Typeof(string), typeof(TextBo圎x), new PropertyMetadata("")) SecurityIdProperty = DependencyProperty.Register("SecurityId", Public static readonly DependencyProperty Return (string)GetValue(SecurityIdProperty)
Passwordbox alternative code#
The following code snippet shows how you could subclass the TextBox and add that property: public class TextBo圎x : TextBox This hypothetical property could be used to identify the object uniquely and attach some security feature (such as making the control read-only based on certain criteria, which I won't further explore here). Nevertheless, this is a very useful and efficient system, which, to most users, ends up looking very similar to any other property system.Īs a simple example, let's imagine a TextBox control that defines a new property to assign a security ID to each instance of the control. In object-terms, this is a bit odd because the values that go with an object are not encapsulated in the object anymore. You can think of this system as an external table of named values that go with a certain object. And those are just a few features.įundamentally, the Dependency Property system is a way to first define a property and register it with the overall Dependency Property system, and then assign values to those properties, at which point the system maintains that value for each object. Another is the ability to define further meta-data, such as what the default value is, or how the property is to behave in binding scenarios. One of these is built-in change notification. The second reason for Dependency Properties is that WPF (and other XAML dialects) requires features that standard properties don't provide. An efficient way is needed to store those properties, especially since many of those properties simply sit there with their default values (a scenario that received special efficiency tuning in the Dependency Property system). Systems like WPF instantiate lots and lots of objects, all of which have lots and lots of properties. Why such a difference? One reason is the matter of efficiency. NET are a language feature that combines a get/set pair of methods with some internally stored value (such as the text of a TextBox), Dependency Properties, while still being accessible through get/set, store their values in an external, highly optimized place. These XAML properties are implemented as “Dependency Properties.” The main difference is that while properties in. What may not be obvious to the casual observer is that in XAML, these properties are slightly different from “normal” properties. This includes elements with properties that can be used to change the appearance or behavior of said elements. In more sophisticated terms, Attached Properties are a feature that allows developers to extend UI objects with arbitrary features in very powerful ways.īut let's start at the beginning: In systems such as WPF (Windows Presentation Foundation) or WinRT (what the industry generally refers to as the “XAML Dialects”), UI elements and controls behave much like you would expect them to behave. In simple terms, these are properties that can be arbitrarily attached to just about any object in the UI hierarchy and allow attaching data that needs to be associated and stored with those objects.
All XAML dialects support a feature that is used mostly by accident, yet goes overlooked for its vast potential: Attached Properties.
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