WPF

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“WPF Interview Questions and Answers will guide us now that Windows Presentation Foundation (WPF) is a graphical subsystem for rendering user interfaces in Windows-based applications. WPF, previously known as Avalon, was initially released as part of .NET Framework 3.0. Designed to remove dependencies on the aging GDI subsystem, so learn more about WPF with the help of this WPF Interview Questions with Answers guide”



57 WPF Questions And Answers

1⟩ What is XBAP?

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.

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2⟩ How can I create Custom Read-Only Dependency Properties?

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)

);

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3⟩ What is WPF?

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.

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4⟩ How can I enumerate all the descendants of a visual object?

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);

}

}

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5⟩ What is XAML extensible markup language?

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.

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6⟩ Is WPF has replaced DirectX?

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.

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7⟩ Define Freezable objects in WPF?

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.

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8⟩ List the types of documents which are supported by WPF?

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.

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9⟩ How can I use an application resource?

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>

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10⟩ How can I set an attached property in code?

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);

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11⟩ How can I mark the default value of a custom dependency property to be false?

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));

}

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14⟩ Why WPF preferred over Adobe Flash?

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.

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15⟩ Can we use Windows Forms in a WPF application?

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.

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18⟩ Define CustomControl briefly?

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.

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20⟩ Explain the difference between Events and Commands in the MVVM model?

Commands are more powerful and are advantageous to use instead of events. Actions are deeply connected with the event's source and, therefore, the events cannot be reused easily. But commands make it possible to efficiently maintain multiple actions at one place and then reuse them as per our requirement.

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