God Blessings TO All the People: WPF Interview Questions :

Questions with Answers :

1 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.

2 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.

3 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.

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);
}
}

5 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)
);

6. What is WPF?

WPF stands for Windows Presentation Foundation. It is an application programming Interface for developing rich UI on Windows. WPF is introduced in .NET 3.0. By the use of WPF we can create two and three dimensional graphics,animations etc.

7. What is XAML and how it is related to WPF?

XAML is a new mark up language which is used for defining UI elements and its relationships with other UI elements. The XAML is introduced by WPF in .NET 3.0 WPF uses XAML for UI design.

8. Does XAML file compiled or Parsed?

By default XAML files are compiled ,But we do have options to let it be parsed.

9. What is the root namespace used for Animations and 3D rendering in WPF?

System.Windows.Media namespace.

10. What are the names of main asseblies used by WPF?

a)WindowsBase
b)PresentationCore
c)PresentationFoundation

11. What operating systems support WPF?

Following are the operating systems that support WPF
a)Windows7
b)Windows Vista
c)Windows XP Service Pack 2 or later

12. Describe the types of documents supported by WPF?

There are two kinds of document supported by WPF
a)Flow format:Flow format document adjusts as per screen size and resolution
b)Fixed Format:Fixed Format document does not adjust as per screen size and resolution

13. What namespaces are needed to host a WPF control in Windows form application?

The following namespaces needs to be referenced :
a)PresentationCore.dll
b)PresentationFramework.dll
c)UIAutomationProvider.dll
d)UIAutomationTypes.dll
e)WindowsBase.dll

14. What is Dependency Property In WPF?

Windows Presentation Foundation (WPF) has a set of services that is used to extend the functionality of a common language runtime property. These services are referred as the WPF property system. A property that is backed by the WPF property system is known as a dependency property

15.What is routed event in WPF?

A WPF user interface is constructed in a layered approach, where one visual element can have zero or more child elements. so we can visualise the elements tree for the full page. Routed events are a new feature provided by WPF which allows events to travel down the elements tree to the target element, or bubble up the elements tree to the root element. When an event is raised, it "travels" up or down the elements tree invoking handlers for that event on any element subscribed to that event it encounters en route.This tree traversal does not cover the entire elements tree, only the ancestral element chain between the root element and the element which is the target of the event.

Ques: 1 
What is a Freezable?

Ans:  A freezable object is one that has a mechanism that allows you to "Freeze" it. This locks downs all the state and makes the object immutable. This makes the object more performant to use and safer to share between threads.

Ques: 2 
What is Path animation?

Ans: Path animation in which the object moves along the path specified by the Path geometry. As the animation progresses, it reads the X-axis, Y-axis and angle information from the path geometry and generates the output. These are useful when an object has to be animated along a complex path.

Ques: 3 
What is the use of System.Windows.Media namespace?

Ans:This is the root namespace of several other media related namespaces. It provides different types to work with animations like 3D rendering, text rendering and other multimedia services.

Ques: 4 
What are the core WPF assemblies?

Ans:The core WPF assemblies are,

WindowsBase.dll:- This is the core types constituting the infrastructure of WPF API.

PresentationCore.dll:- It defines numerous types constituting foundation of WPF GUI layer.

PresentationFoundation.dll:- It defines WPF control types, animation & multimedia support, data binding suport and other WPF services.

  Besides these three libraries WPF also uses an unmanaged binary called milcore.dll which acts as a bridge between WPF assemblies and DirectX runtime layer.

Ques: 5 How to define a button USING XAML?

Ans:To define a button in WPF using XAML, Syntax is given below-

<Button Name="btnName">btnCaption</Button>

Example:-

<Button Name="btnClick">Click Me</Button>


Here the <Button> element specifies the use of the Button class.

Ques: 6 
What is the use of System.Windows.Navigation namespace in WPF?

Ans:This namespace contains different classes for navigation between windows.

Ques: 7 
Which namespace is used to work with 3D in WPF.

Ans:System.Windows.Media.Medi3D namespace is used for working with 3D.

Ques: 8 
What is a Routed event?

Ans:In WPF application it contains many elements. These elements exist in an element tree relationship with each other. A routed event is a type of event that can invoke handlers on multiple listeners in an element tree, rather than just on the object that raised the event.

Ques: 9 
Can you explain how we can separate code and XAML?

Ans:   This is one of the most important features of WPF, separating the XAML from the code to be handled. So designers can independently work on the presentation of the application and developers can actually write the code logic independent of how the presentation is.

Ques: 10 
What kind of documents are supported in WPF?

Ans:   There are two kind of major document supported in WPF Fixed format documents and Flow format document. Fixed format documents look like PDF format. They display content regardless of screen size and resolution. But flow format document adjust depending on screen size and resolution.

Ques: 11 
What are dependency properties?

Ans:These dependency properties belong to one class but can be used in another.
Consider the below code snippet:-


<Rectangle Height="72" Width="131" Canvas.Left="74" Canvas.Top="77" />


Height and Width are regular properties of the Rectangle. But Canvas. Top and Canvas. Left is dependency property as it belongs the canvas class. It is used by the Rectangle to specify its position within Canvas.

Ques: 12 
What is XAML extensible markup language?

Ans: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.

Ques: 13 
What is XBAP?

Ans:XBAP means XAML Browser Application. XBAP allows for WPF applications to be used inside a browser. For this .NET framework is required to be installed on the client system and hosted applications run in a partial trust sandbox environment.

Ques: 14 What is WPF?

Ans:Windows Presentation Foundation (WPF) is the presentation subsystem feature of the .NET Framework 3.0,that provide good design and advance controls. Silverlight is the Subset of WPF. Through WPF we can create Windows and WebBrowser Application.

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