Windows Presentation Foundation (WPF) Interview Questions And Answers

Windows Presentation Foundation (WPF) is the presentation subsystem feature of the .NET Framework 3.0. It is pre-installed in as a part of Windows Vista, It is also available for installation on Windows XP SP2 and Windows Server 2003. It supports the rich User Experiences (UX) that have been made possible by advances in hardware and technology since the GDI based UI architecture was initially designed in the 1980's.

XBAP stands for XAML Browser Application. XBAP allows for WPF applications to be used inside a browser. The .NET framework is required to be installed on the client system. Hosted applications run in a partial trust sandbox environment. They are not given full access to the computer's resources and not all of WPF functionality is available.

XAML is an extensible markup language based on XML. XAML can be thought of as a declarative script for creating .NET 3.0 UI. It is particularly used in WPF as a user interface markup language to define UI elements, data binding, eventing and other features. It is also used in Windows Workflow Foundation (WF), in which the workflows themselves can be defined in XAML code.

You can enumerate all the descendants of a visual object as follows :

[C#]

// Enumerate all the descendants of the visual object.
static public void EnumVisual(Visual myVisual)
{
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(myVisual); i++)
{
// Retrieve child visual at specified index value.
Visual childVisual = (Visual)VisualTreeHelper.GetChild(myVisual, i);

// Do processing of the child visual object.

// Enumerate children of the child visual object.
EnumVisual(childVisual);
}
}

The typical reason for specifying a read-only dependency property is that these are the properties that is used to determine the state, but where the state is defined in a multitude of factors. A typical example for a read-only property is IsMouseHover

This example shows how to 'register' an attached property as read-only. You can use dependency properties on any 'DependencyObject' types.

[C#]
public static readonly DependencyProperty IsBubbleSourceProperty = DependencyProperty.RegisterReadOnly(
"IsBubbleSource",
typeof(Boolean),
typeof(AquariumObject),
new FrameworkPropertyMetadata(false, FrameworkPropertyMetadataOptions.AffectsRender)
);

Here is an example :

[C#]

public class MyStateControl : ButtonBase
{
public MyStateControl() : base() { }
public Boolean State
{
get { return (Boolean)this.GetValue(StateProperty); }
set { this.SetValue(StateProperty, value); }
}
public static readonly DependencyProperty StateProperty = DependencyProperty.Register(
"State", typeof(Boolean), typeof(MyStateControl),new PropertyMetadata(false));
}

The following example shows how you can set an attached property in code.

[C#]

DockPanel myDockPanel = new DockPanel();
CheckBox myCheckBox = new CheckBox();
myCheckBox.Content = "Hello";
myDockPanel.Children.Add(myCheckBox);
DockPanel.SetDock(myCheckBox, Dock.Top);

The following example shows an application definition file. The application definition file defines a resource section (a value for the Resources property). Resources defined at the application level can be accessed by all other pages that are part of the application. In this case, the resource is a declared style. Because a complete style that includes a control template can be lengthy, this example omits the control template that is defined within the ContentTemplate property setter of the style.

[XAML]
<Application.Resources>
<Style TargetType="Button" x:Key="GelButton" >
<Setter Property="Margin" Value="1,2,1,2"/>
<Setter Property="HorizontalAlignment" Value="Left"/>
<Setter Property="Template">
<Setter.Value>

...

</Setter.Value>
</Setter>
</Style>
</Application.Resources>

Two types of the documents supported by Windows Presentation Foundation (WPF) are the Flow format and fixed Format document. Flow format document alters the content to fit the screen size while fixed format document present content irrespective of the screen size.

An object, which has its state locked down, so that it becomes unchangeable, is known as a freezable object. Such objects perform better. It is also safer if they are required to be shared between threads.

No, WPF can never replace DirectX. WPF cannot be used to create games with stunning graphics. WPF is meant to be a replacement for windows form, not DirectX.

One of the major differences is that .NET framework is required for running WPF browser applications on the client machine. But Silverlight runs using only the plug-in. Another point of difference is that applications made in WPF depend on the OS as .NET Framework only runs on Windows. On the other hand, the Silverlight plug-in can be installed on those OSs also, which are not Windows.

It has three objects, namely:
★ SetValue
★ ClearValue
★ GetValue

By overruling the ItemsPanel attribute of StatusBar with a grid. The grid's columns can be appropriately configured to get the desired result.

Yes, Windows form can be used in WPF. Windows form can appear as a WPF pop. The controls of this Window form can be placed besides WPF controls in a WPF page by utilizing the functions of the WindowsFormsHost control that comes preinstalled.

CustomControl widens the functions of existing controls. It consists of a default style in Themes/Generic.xaml and a code file. It is the best way to make a control library and can also be styled or templated.

★ PresentationFoundation
★ WindowsBase
★ PresentaionCore

WPF is a more recent technology and thus has the latest development tools. It supports a broader range of programming languages and has a robust control reuse.

Path animation is a type of animation in which the animated object follows a path set by the Path geometry.

Properties that belong to a specific class but can be used for another are called the dependency properties.

WPF has three types of windows:
★ Normal Window
★ Page Window
★ Navigate Window

Sorting can be done by using a property of the ItemsCollection object. ItemsCollection contains an attribute, SortDescriptions, which holds System.ComponentModel.SortDescription instances. Every SortDescription instance defines how the elements should be sorted and indicates if the sort is descending or ascending.

For instance, this code sorts elements of ContentControl on the basis of their word count property:
myItemsControl.Items.SortDescriptions.Add(new SortDescription("WordCount", ListSortDirection.Descending));

MVC stands for Model-View Controller and.MVVM stands for Model-View ViewModel.

In MVVM, View Model is used instead of a controller. This View Model is present beneath the UI layer. It reveals the command objects and data that the view requires. It acts like a container object from which view gets its actions and data.

It is used whenever a requirement for creating custom user interface arises. It is a drawing object, which gives instructions for making an object. These instructions include opacity etc. of the drawing. The Visual class also bridges the functionalities of WPF managed classes and the MilCore.dll.

An event, which can invoke handlers on more than one listeners present in an element tree, instead of the single object which called the event, is known as a Routed event.