Dot Net Interview Questions and Answers

.Net Framework is a programming platform that supports multiple languages like C, VB.Net, ASP.Net, F, JavaScript, SQL Server, etc. It provides a set of tools to develop rich client applications (desktop, web) using HTML5, CSS, JavaScript, and XML. This technology allows you to build highly interactive websites and mobile apps.

Java is an object-oriented language and was first released by Sun Microsystems in 1995. The main objective of this language is to provide security and reliability. Java also has a strong focus on portability. So it can be used across platforms such as Windows, Linux, Mac OS X, Android devices, etc.

Java is written in source code and compiled into bytecode which is then interpreted by the virtual machine. In contrast, .NET is based on Microsoft’s Common Language Runtime or CLR, which is a virtual machine. .NET uses managed code, which means that all the memory addresses are mapped in process space.

Learning .NET will help you become familiar with the latest developments within the .NET Framework. The knowledge gained through learning .NET can be applied in different fields such as software development, database management, networking, graphics, multimedia, etc.

The .NET Framework consists of two parts – core runtime and common language runtimes. Core runtime includes the class libraries, a garbage collector, a just-in-time compiler, a dynamic linker, a thread pooling mechanism, and a type system. Common language runtimes include C, Visual Basic .NET, JScript, PowerShell, IronPython, IronRuby, F, Boo, etc., .NET Framework 4.0 includes support for asynchronous programming models. You can now use the new Task Parallel Library to execute long-running tasks in parallel.

There are many benefits of using .NET Framework over other technologies. Some of them are listed below:

• .NET Framework is the most secure programming environment available today. Because it runs only in the .NET Framework Virtual Machine (VM), there is no possibility of buffer overflow attacks or cross-site scripting vulnerabilities.
• .NET Framework enables building high-performance systems at a low cost by using existing infrastructure such as the operating system kernel, services, and libraries.
• .NET compiles your program so that it executes faster than the traditional approach.
• .NET supports multitasking, multi-threading, and distributed computing.

Both are great resources to get information about .NET Framework, but they have their own pros and cons. MSDN gives detailed documentation about the .NET Framework. However, it may not cover every aspect of the Framework. On the other hand, Google offers a wide range of search results, including blogs, news articles, forums, wikis, videos, etc.

NET Framework comprises four major components, namely, Class Libraries, BCL (Base Class Library), System Namespace, and the Framework Class Library. They are described briefly here:

Class Libraries: A set of classes that provides data structures and algorithms for various purposes. It contains the following packages:

System Namespaces: Provides a way to organize namespaces in .NET applications.

Frameworks Class Library: This contains the base classes and related interfaces used to create applications. The classes in this library provide an abstraction layer between user code and underlying implementation details. These classes are provided at the application level. This is also known as Application Programming Interface (API). Classes from this package are called API classes.

An EXE file refers to an executable file which has been compiled with Microsoft’s C and VB.NET languages. A DLL is a Dynamic Linked Library. It is used to load other assemblies into memory when you start a process.

The common type system is a part of the .NET Framework that defines rules and semantics for types. It allows developers to write programs that interoperate with each other without worrying about compatibility issues.

The latest version, .NET, supports 16 languages. They are:

• C
• VB.NET
• F
• JScript
• PowerShell
• IronPython
• IronRuby
• Boo
• Lasso
• Groovy
• Visual Basic
• Objective C
• ActionScript 3
• XML
• HTML
• SQL

Common Language Runtime is a virtual machine for executing .NET programs written in any language. It is based on the ECMA-335 standard specification. The runtime includes garbage collection and an execution engine.

In static languages, source code is compiled into object modules during the compilation phase. In dynamic languages, source code is interpreted during run time.

Microsoft developed Component Object Model, a technology that allows software components to reuse across multiple programming environments. COM allows you to create component-based applications.

ASP stands for Active Server Pages. It is one of the oldest web development technologies. ASP pages were originally designed to include server-side scripting features such as loops, forms, and database operations. ASP was based on HTML and JavaScript. With the introduction of Visual Studio, ASP pages became more sophisticated. ASP.Net Web Forms is an evolution of ASP.Net. It uses XML markup language to define the structure of the page.

Role-Based security helps to assign permissions to users according to their roles in your organization. It makes it easy to restrict access to sensitive parts of the system and maintain secure configuration settings.

System.StringBuilder class helps you build strings efficiently. You can use StringBuilder for building text strings and manipulating string objects.

System.String is a generic data type in .NET framework. It represents sequences of characters. It provides methods to get, set, remove, replace, compare and format string values.

Namespace is a logical grouping of classes, interfaces, enumerations, structures, delegates, etc., within a single namespace. It is also a container for symbols (classes, methods, properties).

Assembly is a unit of deployment. It contains all necessary files to deploy the application. An assembly has a unique identifier called its Assembly Name or simply name. This name uniquely identifies the assembly among assemblies having the same name.

There are two types of indexes Clustered index and non-clustered index. A clustered index organizes rows into a physical order. Non-clustered indices do not have a specific physical order. They provide faster searches, but they cannot guarantee the results returned will match the original ordering of the table.

There are three types of memory used in .Net Framework, namely, Heap Memory, Stack Memory & Direct Memory.

Net Framework manages memory using Garbage Collection Methodology. It consists of four phases, i.e., Generation, Marking, Collecting, and Remarking. These steps help in managing memory in .Net framework.

Cookies are small bits of information that are sent between the browser and the server every time the user visits a website. Cookies store information about the user’s preferences and allow the site to identify the user when he or she comes back.

IL stands for Intermediate Language. It is a programming languages that can compile to machine code. IL is often compiled using VB.Net source codes.

Tuples are immutable data structures that store a fixed number of elements inside a single variable. They are similar to arrays, but they don’t allow direct access to array indexes. In .NET language, tuples have been implemented as anonymous types.

HTTPhandler is an interface for handling HTTP requests and responses. It is part of the ASP.NET Web API framework.

HttpModule is one of the important components of ASP.NET MVC. It extends the functionality provided by IIS by implementing custom filters and modules for processing incoming requests.

LINQ stands for Language Integrated Query. It is a query syntax based on method calls and operators that let you easily access relational databases with Microsoft’s Entity Data Model.

A custom control is a class that is derived from Control Class, whereas user control can be implemented as a separate.dll. file.

Polymorphism is an object-oriented concept where multiple objects can be treated equally because of their common characteristics. In polymorphic inheritance, subclass instances share the attributes and behavior of the base class, but the type of data stored in each instance is determined at run time.

There are two types of Polymorphism. You can choose between static or compile-time Polymorphism or dynamic or runtime.

Marshaling is a process of converting unmanaged resources (C/C++) to the managed resource(Object). An example would be the conversion of native string to System.String.

Boxing and unboxing are both forms of casting. But boxing involves the creation of a new object, while unboxing involves retrieval of the existing object.

• The open-Closed Principle (OCP) states that it should be easy to extend classes without altering them.
• The Interface Segregation Principle (ISP) says that each independent module should have its own interfaces and should not depend upon other interfaces.
• The dependency Inversion Principle (DIP) states that high-level modules depend only upon abstractions, and low-level modules depend only upon concrete implementations.
• Liskov Substitution Principle (LSP) says that subclasses must provide the same interface as a superclass.

JIT stands for Just in Time Compiler. JIT compiler converts bytecode into machine code when required. This makes the application run faster than interpreted languages like PHP and Java.

This function writes output directly to the response stream rather than writing to the page’s HTML source code.

Response.Redirect simply redirects to another URL. The difference between this and Response.Redirect Method is that Method returns true if redirection was successful; otherwise, false.

Server.Transfer transfers request to another server. If the requested URI does not exist, then it will return HTTP 404 error message.

Managed code refers to any kind of programming language which has been compiled before execution.

Unmanaged code is a programming language whose compilation doesn’t occur until it is executed. So, it cannot be debugged by the developer.

• Constants are variables declared within the program with no default value.
• They are passed as parameters to functions. They are also used in conditional statements.
• Their scope is local to a method, block, or file.
• When a constant is defined outside a method, they are global constants.
• They are usually initialized to 0 or 1.
• They can be useful when a constant must be defined once at the start of a method.
• There are three ways to declare a constant:-Static-Instance-Parameterized

• Read-only variables can be modified but not assigned values.
• They are treated as immutable objects.
• They are always initialized to their default values.
• They are declared using the const keyword.
• It is not possible to change the name of the read-only variable.
• The creation of instances of read-only variables is not possible.
• The type of read-only variable may be primitive data types such as int, char, etc.
• Read-only variables are useful when the programmer wants to make sure that some values are never changed during the course of program execution.

• Memory-mapped files are virtual disks that map a portion of physical disk space into the process address space.
• They are typically created by the operating system kernel with the help of CPU hardware support.
• They reduce the number of I/O operations needed to access a file.
• In Windows, they are called Virtual Memory Files.
• They are made up of segments that store data on a disk.
• They allow an application to treat a file as though it were stored entirely in the main memory.

• Dispose() is a method that releases all unmanaged resources associated with the current instance of an object.
• It should be invoked whenever you are done working with the object.
• Its purpose is to free resources like handles, sockets, etc.
• Disposing of an object frees its underlying native resource without affecting other references to the same object.
• It ensures that your garbage collector collects the object when it becomes unreachable.

• Finalize() is a special method of a class that is run automatically after an object goes out of scope.
• It is useful in cases where the GC must clean up the object.
• It allows one to release unmanaged resources associated with a class.
• It is similar to the destructor except that it runs at the end of the lifetime of the object instead of being called as part of the normal destruction sequence.

CAS provides security for code running inside .NET Framework. CAS helps protect classes from malicious untrusted code. The following steps are followed to implement CAS :

• A class is marked as ‘codeaccesssecurity.’
• All public methods in this class are decorated with attributes.
• Any assembly containing the above-mentioned class is signed using certificates issued by trusted certificate authorities.
• Only assemblies containing code access security classes will be allowed to execute in .NET Framework.

• Class names should start with either uppercase letter or lowercase letter.
• Namespaces should use PascalCase.
• Methods and properties should follow camel case convention.
• Fields should use the underscore (_ ) suffix.
• Local variables should use the camel case.
• Naming a local variable _ would be considered bad practice as it might lead to confusion.

• Garbage Collection is a mechanism used by .NET runtime to reclaim unused portions of memory.
• When an object is no longer referenced by any reference variable, then it gets collected by the garbage collector.
• Garbage collector works at the level of an entire application.
• GC performs automatic, incremental reclamation of memory.

• The Page directive has been modified since the last request.
• The page contains controls that have their own PostBack event handlers.
• There is a parameter passed to the page which indicates whether the control was posted back.

• The base class library is a set of .NET classes that provide common functionality such as data types, algorithms, cryptography, networking, string manipulation, file system access, database connectivity, exception handling, and more.
• The binary Compatibility Layer is a layer between the CLR and managed applications. This layer ensures binary compatibility of the managed application with the existing versions of the CLR.

Assembly consists of three main components: – Header: Contains information about the assembly, including its metadata and version numbers. – Manifest: Specifies the type libraries, COM interfaces, and other resources linked to the assembly. – DLL: Stores program code, along with references to external assemblies.

As per the official site, “If your application runs well on one platform but poorly on another, then there is probably something wrong with the way you have written your software. You need to fix what is causing the problem before looking for ways to improve performance.”

• You cannot prevent a class from inheriting other classes.
• You can only make sure that a class does not inherit any methods or fields from its derived classes.

• Static Constructor– A static constructor is invoked when an instance of a class is first constructed. The static constructor initializes all static members of the class.
• Default Constructor– A default constructor is automatically generated by the compiler when a new object is instantiated without using a user-defined constructor.
• Parameterized Constructor– Parameterized constructor allows you to specify parameters for a constructor.
• Copy Constructor– Copy constructor copies the current state of an object to a newly allocated object.
• Initialize Constructor– An initialize constructor is called just after a new object is initialized. The purpose of this constructor is to initialize the variables of a class.
• Private Constructor-Private Constructor is used to hide the implementation details of a class.

• Multi-Document Interface (MDI) is an interface provided by Windows operating systems that enables multiple documents to be displayed simultaneously within a single window.
• The term Multi-Document Interface was coined by Microsoft in 1987, but the concept dates back to 1970.

• A single Document Interface (SDI) is an interface that provides a single document display capability.
• This interface is available on older versions of Windows operating systems.

Caching is a technique where data is stored in memory so as to reduce the number of requests to the hard drive. This reduces the load on the hard disk and improves overall system performance.

• Page Caching– Pages are cached in RAM instead of HDD. So, it helps to increase speed.
• Data Caching– Data is cached in RAM instead of being saved in HDD. So, it also increases speed.
• Fragment Caching– Fragments are cached in RAM instead. It helps to decrease the time taken to read data from HDD.

Model View Controller(MVC) pattern is a software architecture design pattern that separates the concerns between presentation logic, model, and business logic.

• Model– It contains code that interacts with domain objects.
• View– It contains the graphical output.
• Controller– It controls communication between models and views.

Model view view model(MVVM)pattern is a software architecture design pattern that separates the concerns between the presentation layer, view, and model.

• Presentation Layer– It handles the GUI, layouts, fonts, colors, etc.
• Business Logic– It deals with the core functionality of the application.
• DAL(Data access layer)– It uses database technology to communicate with the database.
• BL(Business logic)– It deals with business rules.
• UI(User interface)– It deals with user interaction.

• Separation of Concerns: Separate the UI from the Data Access Layer.
• Testability: Test the UI and Business Logic separately.
• Reusability: You can reuse the same code for different projects.
• Flexibility: You can change the way your application is presented at run time.
• Performance: Separating the Presentation Layer from the Domain Layer allows you to use the right tool for the job.

Delegate is a keyword in the C language. It’s a reference type that holds a method signature or other object references. Delegates allow us to encapsulate complex operations into methods, making them easier to use and more reusable. Delegates are first introduced in .Net framework version 2.0.

• Event Handler is handled using delegates.
• When we use the delegate in .net framework, it works like this when an event occurs.

Client-side Validation is used for validating form fields before they are sent over the wire to the server.

Server-Side Validation is used to validate data once it has been received by the server.

• Procedures are defined within classes as member functions. As such, procedures are not only useful for defining new behavior but also serve as entry points for functions.
• A function procedure is a function that returns another function. This means that a function procedure can be called multiple times to return a series of functions.

Stored Procedures are written in SQL and stored on the server-side. They perform batch processing tasks (like insertion, deletion, updating, and so on).

Passport Authentication is used to authenticate users against a central server. It provides strong security for web applications. The main feature of Passport Authentication is the ability to control who can access the site.

Session Management Techniques refer to storing values in memory across requests. These values are usually maintained across HTTP requests and may include variables and cookies.

The Repeater control is one of the most commonly used controls in ASP.NET. A repeater allows you to generate HTML output based on data retrieved from a data source. The data source could be a database table, a list of records, or even XML documents.

Item Template is used to display items of a collection. It displays a specified template with each item in the collection.

AlternatingItemTemplate is used to display alternating rows of data.

A separator Template is used to separate columns within a grid view. It specifies whether a column should be displayed as a header or a footer.

HeaderTemplate is used to specify a row header.

FooterTemplate is used to specify what should appear at the bottom of a page. It is available for GridView and ListView.

Data Templates are used to create custom user interface elements. You define a DataTemplate in XAML markup and bind it to your view model. When the view model changes, the DataTemplate will update automatically.

Execute Scalar is used to execute a command. It runs an action associated with the Command property. Take for example, if you have a Button named “Click Me”, its Command property would be set to an Action delegate containing code that performs some operation when the button is clicked.

ExecuteNonQuery executes a Transact-SQL statement. It sends the statement to the database engine and waits until the result set is returned.

GAC is short for Global Assembly Cache. It’s a shared cache component that enables assemblies to be loaded more quickly by other programs running in the same process.

When using connection pooling, the system maintains a pool of connections between the client application and the database. This helps ensure that there are always available connections in the pool so that they can be shared among multiple clients.

• Globalization refers to the practice of designing software to operate correctly regardless of where it is installed. Globalization is often done to make sure that software is easy to translate into different languages.
• In globalization, developers must take into account several factors, including culture, timezone, currency, etc.

Framework Class Library (FCL) contains all classes that are common across the .NET Framework. As this information to a user is that these classes are offered as part of the Framework, but they also extend beyond the Framework into the .NET Framework itself. The Controller coordinates the flow between these two components.

• The appSettings section in the web.config file is a section that contains configuration information for an application. This section contains a collection of key/value pairs, where the key is the name of the setting, and the value is the setting’s value.
• This section can be used to store information such as the application’s database connection string, authentication information, and other configuration information.
• The appSettings section is a helpful way to keep all of an application’s configuration information in one place.

• Dot NET Core is used for developing web applications and services. It can also be used for developing cross-platform applications.
• Dot NET Core is a lightweight and modular platform that can be used for developing applications with a wide range of architectures.
• Dot NET Core is open source and cross-platform. It can be used for developing applications on Windows, Mac, and Linux.

It includes types for collections, data access, diagnostics, IO, LINQ, networking, security, and more.

• It is a set of class library implementations for .NET Core.
• It includes types for collections, data access, diagnostics, IO, LINQ, networking, security, and more.
• It is open-source and cross-platform.
• It is designed for performance and scalability.
• It is being developed by the .NET Core team at Microsoft.

The IGCToCLR interface is an interface that is used to convert an IGC (Interoperable Graphics Container) to a CLR (Common Language Runtime) object.

• The IGCToCLR interface is used to convert an IGC (Interoperable Graphics Container) to a CLR (Common Language Runtime) object.
• The IGCToCLR interface allows you to create a CLR object from an IGC.
• The IGCToCLR interface is used to access the properties and methods of the CLR object.
• The IGCToCLR interface is used to convert the CLR object back to an IGC.
• The IGCToCLR interface is used to access the properties and methods of the IGC.

Generated SQL scripts are a way to export data from one table in order to import it into another table. SQL scripts are often used for archiving purposes, as well as for generating a data backup in the event of a data disaster.

Here are a few reasons that you might want to generate SQL scripts:

• To back up your database
• To restore a database
• To move a database to a different server
• To generate a script that will create a new database

Multithreading is when multiple threads run in parallel in the same process or in separate processes.

Threads provide concurrency, which is the ability to perform two or more tasks simultaneously. They give you additional control over each individual task compared to single-threaded programming.

You should never run thousands of long-running background operations in a multithreaded program because this would degrade its overall performance. You should always use thread pools instead of creating threads directly.

Asynchronous programming patterns make use of asynchronous programming techniques like Background Workers and Task Parallel Library (TPL). These patterns help programmers develop scalable and resilient solutions without the need to write callback functions or synchronous code.

ErrorProvider control is used for displaying error messages. When you enter invalid text in controls using Error Provider Control, a message appears above the error area with information about the reason. The screen image shows a button and returns to the property page where you can change the appearance of the border when there’s a focus on a more complicated form. This feature helps users find errors quickly in complex forms.

Clone creates a shallow copy of data that uses the original values for all properties except those explicitly set on the cloned object. Each column gets replicated by the clone unless any of these columns contains a reference to another data source.

BindingSource is used to display a large amount of records with small number of fields. When the binding source is used, the user can select a field name in a grid view control, click a button, open a dialog box and edit the contents of the selected row.

Copy makes a deep copy of a dataset. It copies all rows along with their relationships. It includes a full set of changes made to the underlying tables after the copy was executed. If you modify the copied row, the original dataset does not reflect the modifications until you update the original dataset.

PE stands for Portable Executable. A PE file is developed by Microsoft Corporation for Windows operating systems and its an executable file format . A PE file is a very compact binary file format containing only instructions for how to load and execute the file. The main purpose of a PE file is to contain machine-readable code so that programs created in other languages can be loaded and executed on computers running Microsoft’s .Net framework.

Serialization is a process of converting data into a serialized form for storage and transmission across computer networks and other communication channels. It is usually performed to convert objects from one state to another.

Application Object is a singleton class that represents the current instance of your application. Application Object provides access to static variables, constants, and methods defined in this class.

A Thread Pool is a collection of threads that run tasks. A TASK QUEUE is a mechanism through which we can assign jobs to different threads at runtime.

Synchronous Programming Model: Synchronous programming model is based on blocking calls and requires the use of locks.

Asynchronous Programming Model: Asynchronous programming model is based on nonblocking calls and allows multiple threads to perform operations simultaneously without affecting the execution order.