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How WPF Application (Architecture) Works?
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The major components of WPF are
-PresentationFramework,
-PresentationCore, and
-Milcore unmanaged component
Milcore is written in unmanaged
code in order to enable tight integration with DirectX. All display in WPF is done through the DirectX engine, allowing for efficient hardware and software rendering. WPF also required fine control over memory and execution.
The composition engine in milcore is extremely performance sensitive, and required giving up many advantages of the CLR to gain performance.
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what is routed events?
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Routed events are events which navigate up or down the visual tree according to their RoutingStrategy. The routing strategy can be bubble, tunnel or direct. You can hook up event handlers on the element that raises the event or also on other elements above or below it by using the attached event syntax: Button.Click="Button_Click".
Routed events normally appear as pair. The first is a tunneling event called PreviewMouseDown and the second is the bubbling called MouseDown. They don't stop routing if the reach an event handler. To stop routing then you have to set e.Handled = true;
Tunneling The event is raised on the root element and navigates down to the visual tree until it reaches the source element or until the tunneling is stopped by marking the event as handeld. By naming convention it is called Preview... and appears before corresponding bubbling event.
Bubbling The event is raised on the source element and navigates up to the visual tree until it reaches the root element or until the bubbling is stopped by marking the event as handled. The bubbling event is raised after the tunneling event.
Direct The event is raised on the source element and must be handled on the source element itself. This behavior is the same as normal .NET events.
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What are Value Converters?
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A value converter converts one type to another. Converters are frequently used in data binding scenarios where the target type and the source type are not the same. Value converters are used heavily in WPF because XAML attributes are strings, but these strings often need to be converted into objects. For instance, thestring value of red for a background in XAML needs to be converted to a Color object representing red.
If you want to databind two properties that have incompatible types, you need a piece of code in between, that converts the value from source to target type and back. This piece of code is called ValueConverter. A value converter is a class, that implements the simple interface IValueConverter with the two methods object Convert(object value) andobject ConvertBack(object value).
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What is the difference between X:name and x:key?
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X:name idetifies a UIElment in XAML Tree
X:Key identifies objects in resources section, can be accessed by resourceDictionary
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Explain WPF’s 2-Pass layout engine?
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In some cases, an element may know exactly what size it should be (because it’s Width and Height properties have been explicitly set). But very often, the size of an element is determined by its content. To enable this “size to content” feature, the WPF layout engine uses a 2-pass layout cycle to size and position visual elements:
1. First a measure pass is used to determine the desired size of each element.
2. Then an arrange pass is used to explicitly size and position each element.
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What is the difference between Logical Tree and Visual Tree?
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Logical Tree:
XAML is natural for representing a user interface because of its hierarchical nature. In WPF, user interfaces are constructed from a tree of objects known as a logical tree
Visual Tree:
A similar concept to the logical tree is the visual tree. A visual tree is basically an expansion of a logical tree, in which nodes are broken down into their core visual components. Rather than leaving each element as a "black box," a visual tree exposes the visual implementation details.
Window's default visual tree consists of a Border, AdornerDecorator, two AdornerLayers, a ContentPresenter, and nothing more
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