Top 100+ Mvvm Interview Questions And Answers
Question 1. What Is Mvvm?
Answer :
The Model, View, ViewModel (MVVM sample) is all approximately guiding you in a way to arrange and structure your code to put in writing maintainable, testable and extensible applications.
Question 2. What Are The Logical Layers Of Mvvm?
Answer :
Model − It honestly holds the facts and has not anything to do with any of the enterprise common sense.
ViewModel − It acts as the link/connection between the Model and ViewModel, and makes stuff appearance pretty.
View − It surely holds the formatted date and basically delegates the whole thing to the Model.
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Question three. What Are The Benefits Of Mvvm?
Answer :
The key gain is allowing real separation between the View and Model beyond reaching separation and the efficiency that you advantage from having that. What it manner in real terms is that after your model desires to change, it is able to be changed without problems without the view needing to and vice-versa.
There are 3 key things that glide out of making use of MVVM:
Maintainability.
Testability.
Extensibility.
Question four. What Are The Disadvantages Of Mvvm?
Answer :
Some human beings think that for easy UI, MVVM may be an overkill.
Similarly in larger instances, it may be hard to layout the ViewModel.
Debugging might be a bit tough when we've got complicated statistics bindings.
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Question 5. What Are The Responsibilities Of Model?
Answer :
In widespread, version is the only one to understand. It is the customer facet data version that supports the perspectives in the application.
It is composed of objects with houses and some variables to incorporate statistics in memory.
Some of those residences may additionally have reference to other version objects and create the object graph which as an entire is the model objects.
Model gadgets have to enhance property trade notifications
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Question 6. Which In Wpf Means Data Binding?
Answer :
The closing obligation is validation that's optional, however you may embed the validation data on the version items by the usage of the WPF data binding validation capabilities through interfaces like INotifyDataErrorInfo/IDataErrorInfo.
Question 7. What Are The Responsibilities Of View?
Answer :
The essential purpose and responsibilities of perspectives is to outline the shape of what the user sees at the display screen. The structure includes static and dynamic components.
• Static parts are the XAML hierarchy that defines the controls and layout of controls that a view consists of.
• Dynamic component is like animations or state changes which can be described as part of the View.
• The primary intention of MVVM is that there ought to be no code in the back of inside the view.
• In view you as a minimum need the constructor and a name to initialize element.
• The occasion managing, motion and facts manipulation common sense code shouldn’t be within the code at the back of in View.
• There are also other styles of code that must cross in the code behind any code it's required to have a connection with UI element. It is inherently view code.
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Question eight. What Are The Responsibilities Of Viewmodel?
Answer :
ViewModel is the primary factor of MVVM software. The number one responsibility of ViewModel is to offer data to the view, so that view can put that records at the display screen.
It additionally lets in the user to have interaction with facts and change the statistics.
The different key obligation of ViewModel is to encapsulate the interplay logic for a view, but that doesn't suggest all the logic of the utility have to pass into ViewModel.
It need to be capable of handle the proper sequencing of calls to make the proper issue appear primarily based on person or any changes at the view.
ViewModel must also manage any navigation good judgment like finding out when it's time to navigate to a one of a kind view.
Question nine. How Many Ways Are Used To Construct Views?
Answer :
There are ways to construct perspectives. You can use any individual of them.
View First Construction in XAML
View First Construction in Code-at the back of
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Question 10. What Is View First Construction In Xaml?
Answer :
One manner is to sincerely add your ViewModel as a nested element in the setter for the DataContext assets as shown inside the following code.
<UserControl.DataContext>
<viewModel:StudentViewModel/>
</UserControl.DataContext>
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Question eleven. What Is The View First Construction In Code-in the back of?
Answer :
Another manner is that you may do view first creation through honestly constructing the view version your self inside the code behind of your View by setting the DataContext assets there with the instance.
Typically, the DataContext belongings is ready within the constructor method of view, however you could also defer the construction until the Load occasion of the view fires.
Using System.Windows.Controls;
namespace MVVMDemo.Views
/// <summary>
/// Interaction logic for StudentView.Xaml
/// </summary>
public partial class StudentView : UserControl
public StudentView()
InitializeComponent();
this.DataContext = new MVVMDemo.ViewModel.StudentViewModel();
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Question 12. What Is The Main Reason Of Constructing Viewmodel In Code-behind?
Answer :
The important cause of building ViewModel in code-behind rather than XAML is that the view model constructor takes parameters, however XAML parsing can handiest construct elements if described in default constructor.
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Question 13. What Is The Key Feature That Differentiates Mvvm From Other Ui Separation Patterns Like Mvc And Mvp?
Answer :
Data binding is the important thing function that differentiates MVVM from other UI separation patterns like MVC and MVP.
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Question 14. In How Many Ways Can You Bind Data?
Answer :
Data bindings can both be OneWay or TwoWay to flow statistics from side to side between the View and ViewModel.
Question 15. How Viewmodel First Construction Approach Leverages The Capabilities Of Implicit Data Templates In Wpf?
Answer :
Implicit information templates can robotically pick out the proper template from the modern aid dictionary for an element that makes use of statistics binding. They do this based at the type of the statistics item that's rendered by using records binding. First you want to have some element that is binding to a information item.
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Question sixteen. What Are The Responsibilities Of Invoker And Receiver In Command Pattern?
Answer :
There are principal actors, the invoker and the receiver in Command pattern.
Invoker : Invoker is a chunk of code which can execute some vital good judgment. Typically, it's miles a UI detail that the person interacts with in the context of a UI framework. But it could just be any other chunk of logic code elsewhere inside the utility.
Receiver : Receiver is the logic this is intended for execution when the invoker fires. In the context of MVVM, the receiver is commonly a method to your ViewModel that wishes to be referred to as.
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Question 17. What Is Delegate Command?
Answer :
In between the invoker and the receiver you've got an obstruction layer that does not permit the invoker and the receiver to explicitly understand about every different. This is generally represented as an interface abstraction uncovered to the invoker and a concrete implementation of that interface is able to calling the receiver.
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Question 18. Does Each And Every Piece Of Child Content That You Separate Into Its Own Xaml File Necessarily Needs To Be An Mvvm View?
Answer :
No, if the chunk of content just provides the structure to render something to the screen and does now not support any input or manipulation by means of the user for that content material. It may not need a separate ViewModel, but it may simply be a piece XAML that renders primarily based on residences uncovered by the mother and father ViewModel.
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Question 19. What Is Validation In Mvvm?
Answer :
When your software starts offevolved accepting statistics input from end users you want to do not forget validating that input. To ensure it conforms for your average requirements.
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Question 20. In How Many Ways Can You Express Validation?
Answer :
You can use the subsequent ways of expressing validation which can be supported by using WPF statistics binding:
Throwing exceptions on a property is set.
Implementing the IDataErrorInfo interface.
Implementing INotifyDataErrorInfo.
Use WPF validation rules.
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Question 21. What Is Dependency Injection / Ioc Containers?
Answer :
Inversion of Control (IoC) and dependency injection are two design patterns that are carefully associated and the box is essentially a bit of infrastructure code that does each of those patterns for you. IoC pattern is ready delegating duty for creation and the dependency injection sample is set supplying dependencies to an item it is already been built.
Question 22. What Is An Event?
Answer :
An event is a programming assemble that reacts to a alternate in kingdom, notifying any endpoints that have registered for notification. Primarily, events are used to inform a user input via the mouse and keyboard, however their usefulness is not confined to that. Whenever a country exchange is detected, possibly while an object has been loaded or initialized, an occasion may be fired to alert any involved 1/3 events.
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Question 23. What Is Icommand?
Answer :
ICommand defines a command The ICommand kind exposes the subsequent individuals.
CanExecute :Defines the method that determines whether the command can execute in its contemporary nation.
Execute :Defines the method to be referred to as when the command is invoked.
CanExecutehanged :Occurs whilst adjustments arise that have an effect on whether or not the command must execute
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Question 24. What Are Advantages Of Mvvm Over Mvc?
Answer :
Increases the “Blendability” of your perspectives (capability to use Expression Blend to layout views) – This allows a separation of responsibilities on teams which might be fortunate enough to have a fashion designer and a programmer… every can paintings unbiased of the other.
“Lookless” view logic – Views are agnostic from the code that runs at the back of them, allowing the same view common sense to be reused throughout multiple perspectives or have a view without difficulty retooled or changed. Seperates concerns between “behavior” and “fashion”.
No duplicated code to update perspectives – In code-at the back of you may see a variety of calls to replace view controls. With MVVM you may be confident the view is up to date accurately simply via putting the underlying assets and all view facet-results thereof.
Testability – Since your logic is absolutely agnostic of your view, unit testing is made smooth. You can take a look at the behavior of a ViewModel with out regarding its view. This additionally enabled check-pushed improvement of view conduct, which is nearly impossible the usage of code-behind.
Designer-Developer Workflow – MVVM facilitates a separation of UI and presentation logic issues from the business layer that makes it smooth to streamline the development manner by allowing design cycles to manifest in parallel with development.
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Question 25. What Is Inotifypropertychanged?
Answer :
The INotifyPropertyChanged interface is used to inform clients, commonly binding clients, that a property cost has changed.For example, consider a Stock item with a property known as StockCount.
To offer normal property-exchange notification, the Stock type implements the INotifyPropertyChanged interface and raises a PropertyChanged occasion whilst StockCount is modified.For change notification to arise in a binding among a certain customer and a information source, your bound type should either:
Implement the INotifyPropertyChanged interface (favored).
Provide a trade occasion for every property of the sure type.
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Question 26. Why We Need Mmvm?
Answer :
MVVM enables a clear separation of the development of the UI from the development of the enterprise logic or returned end good judgment known as the version (additionally referred to as the facts version to distinguish it from the view version). The view model of MVVM is a price converter. MVVM become designed to make use of records binding capabilities in WPF to higher facilitate the separation of view layer development from the relaxation of the sample through doing away with definitely all GUI code (“code-in the back of”) from the view layer.
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