Xamarin Interview Questions

13) What is Data Binding in Xamarin?

Data binding is a technique to automatically synchronize a user interface with its data source. When a binding is established and the data or your business model changes, then it reflects the updates automatically to the UI elements and vice versa.

Data binding connects two objects, called the source and the target. The source object provides the data. The target object, which must be a bindable property, will consume (and often display) data from the source object. It is also possible to bind, not to a standard data source, but to another element on the page.

14) What are different type of Data Binding modes in Xamarin?

Data binding connects two objects, called the source and the target. So the relationship between target and source is defined by members of the BindingMode enumeration and there is four kinds of binding modes are available in Xamarin.Forms.

• Default (Optional & not considered)
• OneWay — changes in the source affect the target (normal).
• OneWayToSource — changes in the target affect the source.
• TwoWay — changes in the source and target affect each other.

15) What is Views?

Views are commonly known as controls of widgets. And they can refer to visual objects such as Label, Button, Entry, Image, BoxView, ListView, TableView..etc.

16) How many ways can we share the code?

TThere are three ways we can share code:

Shared Project: Here, if required, we write platform specific code using #if compiler directives.

Portable Class Libraries: Here, we create a PCL targeting the platforms we wish to support and then we use Interfaces & Dependency Services to use platform specific functionality. .NET Standard Libraries: It works similar to the PCL and requires Interfaces to work with platform specific functionality.

17) What are Triggers? How many types of Triggers are available?

Triggers allow us to declare actions in XAML which changes the appearance of the control when specific condition is met for specific control property or specific event is raised.
We can add triggers to the control-level, page-level or application-level in the resource dictionary. There are four types of Triggers.
Property Trigger: executed when a property on a control is set to a particular value

• Data Trigger: It is similar to the property trigger but it leverages the use of data binding
• Event Trigger: occurs when some specified event is raised on the control
• Multi Trigger: allows multiple trigger conditions to be set before an action occurs

18) Why Xaml in Xamarin.Forms?

XAML (Extensible Application Markup Language) allows developers to define user interfaces in Xamarin.Forms applications using markup rather than code.
XAML defines the visual appearance of a UI, and an associated code-behind file defines the logic. The UI design can be adjusted without necessarily making changes to the logic in code-behind. XAML in this role simplifies the workflow between individuals who might have a primary visual design responsibility and individuals who are responsible for app logic and information design.

19) What is ResourceDictionary?

ResourceDictionary is used to define the XAML Resources which can be re-used more than once throughout the Xamarin.Forms application.
XAML resources are the definition of objects which can be used more than once.
ResourceDictionary allows all such resource objects declared at one place.
Generally, we can define Styles, ControlTemplates, DataTemplates, Colors and Converters into the ResourceDictionary.
In XAML, these resources can be accessed using the StaticResource Markup Extension.
ResourceDictionary can be declared at either Element Level (inside specific Element), Page Level (inside Page) or Application Level (inside App.xaml).

20) What is difference between Margin & Padding property?

Margin is applied to the outside of you element hence effecting how far your element is away from other elements. Padding is applied to the inside of your element hence effecting how far your element’s content is away from the border.

21) What is Cell in Xamarin.Forms?

Simple it is not a visual element, but it just describes a template for creating a visual element. And one important note is that Cells are elements designed to be added to ListView or TableView controls.

22) What is Xamarin.Android?

Xamarin.Android allows us to create native Android applications using the same UI controls we would in Java,except with the flexibility and elegance of a modern language(C#),the power of the .NET Base Class Library(BCL).

23) Can we develop Windows mobile application using xamarin Studio in mac OS?

No.We need Windows machine for develop windows based application.

24) What is use of MOBILE conditional compilation?

Xamarin projects always define MOBILE Which is true for both iOS and Android application projects

25) What is the difference between Xaml & axml in Xamarin Technology?

• AXML and XAML are two different XML specifications.
• AXML is just supported/available for Xamarin.Android.
• XAML is the way Xamarin Forms could standardize Cross Platform UI based on XML specification.
• XAML is the way Xamarin Forms could standardize Cross Platform UI based on XML specification.
• If you are using native Xamarin Android you will do UI using axml, if using Forms then using XAML.

26) Why we need to use Model-View-ViewModel(MVVM) pattern in Xamarin?

The Model-View-ViewModel pattern can be used on all XAML platforms. Its intent is to provide a clean separation of concerns between the user interface controls and their logic.

27) Name few widely used Layout Controls

• Frame: It contains a single element as a child having a default padding of 20.
• Grid: It is used when UI components are to be arranged into Rows & Columns.
• StackLayout: It is used when UI components are to be arranged either horizontally or vertically.
• ScrollView: It enables the scrolling for a child element if required. It has one child only.
• There are other Layout Controls too like AbsoluteLayout, RelativeLayout, ContentView, ContentPresenter, etc.

28) What are the life cycle’s of Xamarin.forms app development?

• Life-Cycle means a specific sequence of the application from start to finish of the application. So there are three important states in the life cycle of a Xamarin app development.
• OnStart: Called when the application starts.
• OnSleep: Called each time the application goes to the background.
• OnResume: Called when the application is resumed, after being sent to the background.

29) What does Pages in Xamarin.Forms?

The Page class is a visual element that occupies most or all of the screen and contains a single child. And pages in xamarin.forms are directly mapped to like below:

1. In iOS it is a View Controller
2. In Windows Phone it is a Page.
3. In Android it is a Activity.

30) What is NuGet and how it can help in Xamarin App Development?

NuGet is the most popular package manager for .NET development. It is built in to Xamarin Studio 5 and Visual Studio. You can easily search for and add packages/third party libraries to your Xamarin.Forms using either IDE.