.NET and WPF BASIC INTERVIEW QUESTIONS

What is WPF

WPF stands for Windows Presentation Foundation. It is a graphical subsystem of the Microsoft .NET framework for creating desktop applications with visually stunning user interfaces. WPF provides a unified programming model for building desktop applications, combining application logic, documents, media, and user interface into a single framework.

Key features of WPF include:

1. XAML (eXtensible Application Markup Language): WPF uses XAML as a markup language to define the user interface elements, layouts, and interactions.

2. Data Binding: WPF provides powerful data binding capabilities, allowing developers to easily bind data from various sources to UI elements.

3. Styles and Templates: WPF enables the creation of reusable styles and templates for consistent and customizable UI design.

4. Graphics and Multimedia Support: WPF offers rich graphics and multimedia capabilities, including support for 2D and 3D graphics, animation, audio, video, and vector graphics.

5. Layout Management: WPF provides flexible and dynamic layout management through various layout panels, allowing responsive UI design.

6. Commanding and Input: WPF includes a commanding system that enables the creation and handling of user commands. It also supports various input methods, including keyboard, mouse, touch, and stylus.

7. Accessibility: WPF has built-in accessibility features to ensure applications are accessible to users with disabilities.

WPF applications can be developed using programming languages such as C# or VB.NET and can run on Windows-based systems. It provides a powerful and versatile framework for building modern desktop applications with visually appealing user interfaces and interactive functionality.

WPF advantages

• It's newer and thereby more in tune with current standards
• Microsoft is using it for a lot of new applications, e.g. Visual Studio
• It's more flexible, so you can do more things without having to write or buy new controls
• When you do need to use 3rd party controls, the developers of these controls will likely be more focused on WPF because it's newer
• XAML makes it easy to create and edit your GUI, and allows the work to be split between a designer (XAML) and a programmer (C#, VB.NET etc.)
• Databinding, which allows you to get a more clean separation of data and layout
• Uses hardware acceleration for drawing the GUI, for better performance
• It allows you to make user interfaces for both Windows applications and web applications (Silverlight/XBAP)

 What is .NET?

.NET is a software development framework developed by Microsoft. It provides a controlled environment for developing and running applications. It supports multiple programming languages and allows developers to build applications for various platforms, including Windows, web, mobile, and more.

Introduction to .NET and .NET Core Framework

.NET framework is developed by Microsoft, provides an environment to run, debug and deploy code onto web services and applications by using tools and functionalities like libraries, classes, and APIs. This framework uses object-oriented programming.

You can use different languages like C#, Cobol, VB, F#, Perl, etc. for writing .NET framework applications. This Framework supports services, websites, desktop applications, and many more on Windows. It provides functionalities such as generic types, automatic memory management, reflection, concurrency, etc. These functionalities will help to make the development easier and efficiently build high-quality web as well as client applications.

.NET Core is a newer version of the .NET framework and it is a general-purpose, cost-free, open-source development platform developed by Microsoft. .NET Core is a cross-platform framework that runs an application on different operating systems such as Windows, Linux, and macOS operating systems. This framework can be used to develop various kinds of applications like mobile, web, IoT, cloud, microservices, machine learning, game, etc.

Characteristics of .NET Core:

Free and open-source: .NET Core source code project can be obtained from Github. It is free and licensed under the MIT and Apache licenses.

Cross-platform: .NET Core is supported by different operating systems like Windows, macOS, and Linux.

Sharable: A single consistent API model that is written in .NET Standard will be used by .NET Core and is common for all the .NET applications. The same library or API can be used on multiple platforms with different languages.

Friendly: The .NET Core is compatible with .NET Framework, Mono, and Xamarin, through .NET Standard. It also supports working with different Web frameworks and libraries such as Angular, React, and JavaScript.

Fast: .NET Core 3.0 is faster compared to the .NET Framework, .NET Core 2.2 and previous versions. It is also much faster than other server-side frameworks like Node.js and Java Servlet.

What are the key components of .NET?

The key components of .NET include:

Common Language Runtime (CLR): It is the runtime environment that manages code execution and provides services like memory management, exception handling, and security.

.NET Framework Class Library (FCL): It is a collection of reusable classes, interfaces, and types that developers can use to build applications.

Languages: .NET supports multiple programming languages such as C#, VB.NET, F#, and more.

Tools: Visual Studio is the primary development tool for .NET applications.

 How does the .NET framework work?

.NET framework-based applications that are written in supportive languages like C#, F#, or Visual basic are compiled to Common Intermediate Language (CIL).

Compiled code is stored in the form of an assembly file that has a .dll or .exe file extension.

When the .NET application runs, Common Language Runtime (CLR) takes the assembly file and converts the CIL into machine code with the help of the Just In Time(JIT) compiler.

Now, this machine code can execute on the specific architecture of the computer it is running on.

Common Language Runtime(CLR):

It is an execution engine that runs the code and provides services that make the development process easier.

Services provided by CLR are memory management, garbage collection, type safety, exception handling, security, and thread management. It also makes it easier for designing the applications and components whose objects interact across the languages.

The programs written for the .NET Framework are executed by the CLR regardless of programming language. Every .NET Framework version is having CLR. 

Framework Class Library(FCL):

It has pre-defined methods and properties to implement common and complex functions that can be used by .NET applications. It will also provide types for dates, strings, numbers, etc.

This class library includes APIs for database connection, file reading and writing, drawing, etc.

 

Common Type System(CTS):

CTS specifies a standard that will mention which type of data and value can be defined and managed in memory during runtime.

It will make sure that programming data defined in different languages should interact with each other for sharing the information. For example, in VB.NET we define datatype as integer, while in C# we define int as a data type.

It can be used to prevent data loss when you are trying to transfer data from a type in one language to its equivalent type in another language.

Common Language Specification (CLS):

Common Language Specification (CLS) is a subset of CTS and defines a set of rules and regulations to be followed by every .NET Framework’s language.

A CLS will support inter-operability or cross-language integration, which means it provides a common platform for interacting and sharing information. For example, every programming language(C#, F#, VB .Net, etc.) under the .NET framework has its own syntax. So when statements belonging to different languages get executed, a common platform will be provided by the CLS to interact and share the information.

What is CTS?

CTS stands for Common Type System. It follows a set of structured rules according to which a data type should be declared and used in the program code. It is used to describe all the data types that are going to be used in the application.

We can create our own classes and functions by following the rules in the CTS. It helps in calling the data type declared in one programming language by other programming languages.

Explain CLS

Common Language Specification (CLS) helps the application developers to use the components that are inter-language compatible with certain rules that come with CLS. It also helps in reusing the code among all of the .NET-compatible languages

What is JIT?

JIT stands for Just In Time. It is a compiler that converts the intermediate code into the native language during the execution.

What is the difference between .NET Framework, .NET Core, and .NET 5+?

The .NET Framework is a Windows-only framework that has been around for many years. It is used for building Windows desktop applications, ASP.NET Web Forms, and other types of applications.

.NET Core is a cross-platform framework designed for building modern, cloud-based applications that can run on Windows, macOS, and Linux. It also includes a subset of the .NET Framework called the .NET Standard.

Starting with .NET 5, Microsoft unified the .NET Framework and .NET Core into a single framework called .NET 5 and later versions. This unified framework supports cross-platform development and provides a consistent set of APIs for building applications.

What is C#?

C# (pronounced C sharp) is a modern, object-oriented programming language developed by Microsoft. It is one of the primary languages used for developing .NET applications. C# combines the power of C++ with the simplicity of Visual Basic. It is designed to be simple, type-safe, and efficient.

What is the difference between int and Int32?

There is no difference between int and Int32. Int32 is a type provided by the .NET framework class whereas int is an alias name for Int32 in the C# programming language.

 What are the different types of memory in .NET?

In .NET, there are mainly two types of memory:

Stack: It is used for storing value types, method parameters, and local variables. The memory allocated on the stack is automatically freed when it goes out of scope.

Heap: It is used for storing reference types and dynamically allocated memory. The memory allocated on the heap needs to be explicitly freed by the garbage collector.

What is garbage collection in .NET?

Garbage collection is an automatic memory management process in .NET. It is responsible for reclaiming memory that is no longer in use by the application. The garbage collector identifies and frees objects that are no longer reachable, freeing up memory for future use. Developers don't need to manually deallocate memory in .NET.

These are just a few basic .NET interview questions and answers. The actual depth and breadth of the questions can vary depending on the level of the interview and the specific requirements of the job.

The main differences between value type and

reference type are given below:

A Value Type holds the actual data directly within the memory location and a reference type contains a pointer which consists of the address of another memory location that holds the actual data.

Value type stores its contents on the stack memory and reference type stores its contents on the heap memory.

Assigning a value type variable to another variable will copy the value directly and assigning a reference variable to another doesn’t copy the value, instead, it creates a second copy of the reference.

Predefined data types, structures, enums are examples of value types. Classes, Objects, Arrays, Indexers, Interfaces, etc are examples of reference types

Explain Microsoft Intermediate Language

MSIL is the Microsoft Intermediate Language, which provides instructions for calling methods, memory handling, storing and initializing values, exception handling, and so on.

The instructions provided by MSIL are platform-independent and are generated by the language-specific compiler from the source code. JIT compiler compiles the MSIL into machine code based on the requirement

What is an assembly?

An assembly is a file that is automatically generated by the compiler which consists of a collection of types and resources that are built to work together and form a logical unit of functionality. We can also say, assembly is a compiled code and logical unit of code.

Assemblies are implemented in the form of executable (.exe) or dynamic link library (.dll) files

What are the basic data types in C#?

The basic data types in C# are:

1. bool: Represents a Boolean value (true or false).
2. byte: Represents an 8-bit unsigned integer.
3. sbyte: Represents an 8-bit signed integer.
4. short: Represents a 16-bit signed integer.
5. ushort: Represents a 16-bit unsigned integer.
6. int: Represents a 32-bit signed integer.
7. uint: Represents a 32-bit unsigned integer.
8. long: Represents a 64-bit signed integer.
9. ulong: Represents a 64-bit unsigned integer.
10. float: Represents a single-precision floating-point number.
11. double: Represents a double-precision floating-point number.
12. decimal: Represents a decimal number with 28 significant digits.
13. char: Represents a single Unicode character.
14. string: Represents a sequence of Unicode characters. 

What is the default value of a bool variable in C#?

The default value of a bool variable in C# is false.

What is the default value of an int variable in C#?

The default value of an int variable in C# is 0.

What is the difference between int and long data types in C#?

Both int and long are integer data types in C#, but int is a 32-bit signed integer, while long is a 64-bit signed integer. This means that int can store values from -2,147,483,648 to 2,147,483,647, while long can store values from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807. 

What is signed integer and unsigned integer?

A signed integer is a data type that can represent both positive and negative values. It uses a sign bit (usually the most significant bit) to indicate the sign of the value. In C#, the int, long, short, sbyte data types are all signed integers.

An unsigned integer is a data type that can represent only non-negative values. It does not use a sign bit to indicate the sign of the value. In C#, the uint, ulong, ushort, and byte data types are all unsigned integers.

The range of values that can be represented by a signed integer and an unsigned integer is different. For example, an 8-bit signed integer (sbyte) can represent values from -128 to 127, while an 8-bit unsigned integer (byte) can represent values from 0 to 255. It's important to choose the appropriate data type based on the range of values that you need to represent.

What is the difference between a content control 

and an items control in WPF?

Content controls are used to display a single piece of content, while items controls are used to display a collection of items. Content controls include controls such as Label and ContentPresenter, while items controls include controls such as ListBox and ListView.

How do you data bind a control in WPF?

You can data bind a control in WPF by setting its DataContext property to a data object or collection, and then using XAML or code to specify the binding source and path for the control's data properties. You can also use data templates to define the appearance of the bound data.