Top 54 ASP.NET Interview Questions And Answers

Question 1

What is `ViewData`?

Accepted Answer

**ViewData** contains the key, value pairs as dictionary and this is derived from class  `ViewDataDictionary`. In action method we are setting the value for viewdata and in view the value will be fetched by typecasting.

Question 2

What is ASP.NET Core?

Accepted Answer

ASP.NET Core is a brand new cross-platform web framework built with .NET Core framework. It is not an update to existing ASP.NET framework. It is a complete rewrite of the ASP.NET framework. It works with both .NET Core and .NET Framework.

Main characterestics of ASP.NET Core:

*   DI Container which is quite simple and built-in. You can extend it with other popular DI containers
*   Built-in and extensible structured logging. You can redirect output to as many sources as you want (file, Azure, AWS, console)
*   Extensible strongly typed configuration, which can also be used to reload at run-time
*   Kestrel – new, cross-platform and super fast web server which can stand alone without IIS, Nginx or Apache
*   New, fully async pipeline. It is easily configured via middleware
*   ASP.NET All meta package which improves development speed, and enables you to reference all Microsoft packages for ASP.NET Core and it will deploy only those that are being used by your code
*   There is no _web.config_. We now use _appsettings.json_ file in combination with other sources of configuration (command line args, environment variables, etc.)
*   There is no _Global._asax – We have _Startup.cs_ which is used to set up Middleware and services for DI Container.

Question 3

Explain startup process in ASP.NET Core?

Accepted Answer

Everything starts from Program.cs
```csharp
public static void Main(string[] args)
{
    BuildWebHost(args).Run();
}
 
public static IWebHost BuildWebHost(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        .UseStartup<Startup>()
        .Build();
```

CreateDefaultBuilder extension method will create a default configuration which will look first into `appsettings.json` files then will look for Environment variables and at the end, it will use command line arguments.

This part will also set up default logger sources (debug and console) and load the settings for logging from appsettings.json.

After the `CreateDefaultBuilder` finishes, then `Startup` class is executed. First, the constructor code is executed. After that, services are added to DI container via `AddServices` method that lives in Startup class. After that, an order of middleware that will handle every incoming request is set up.

Question 4

Can ASP.NET Core work with the .NET framework?

Accepted Answer

Yes. This might surprise many, but ASP.NET Core works with .NET framework and this is officially supported by Microsoft.

ASP.NET Core works with:

*   .NET Core framework
*   .NET framework

Question 5

What is the difference between ASP.NET and ASP.NET MVC?

Accepted Answer

ASP.NET, at its most basic level, provides a means for you to provide general HTML markup combined with server side "controls" within the event-driven programming model that can be leveraged with VB, C#, and so on. You define the page(s) of a site, drop in the controls, and provide the programmatic plumbing to make it all work.

ASP.NET MVC is an application framework based on the Model-View-Controller architectural pattern. This is what might be considered a "canned" framework for a specific way of implementing a web site, with a page acting as the "controller" and dispatching requests to the appropriate pages in the application. The idea is to "partition" the various elements of the application, eg business rules, presentation rules, and so on.

Think of the former as the "blank slate" for implementing a site architecture you've designed more or less from the ground up. MVC provides a mechanism for designing a site around a pre-determined "pattern" of application access, if that makes sense. There's more technical detail to it than that, to be sure, but that's the nickel tour for the purposes of the question.

Question 6

What is a _postback_?

Accepted Answer

A **postback** originates from the client browser. Usually one of the controls on the page will be manipulated by the user (a button clicked or dropdown changed, etc), and this control will initiate a _postback_. The state of this control, plus all other controls on the page (known as the View State) is Posted Back to the web server.

Question 7

What is _Generic Host_ in .NET Core?

Accepted Answer

The [.NET Generic Host](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/host/generic-host) is a feature which sets up some convenient patterns for an application including those for [dependency injection (DI)](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/dependency-injection), [logging](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/logging), and [configuration](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration). It was originally named Web Host and intended for Web scenarios like ASP.NET Core applications but has since been generalized (hence the rename to _Generic_ Host) to support other scenarios, such as Windows services, Linux daemon services, or even a console app.

A _host_ is an object that encapsulates an app’s resources, such as:

- Dependency injection (DI)
- Logging
- Configuration
- `IHostedService` implementations

Question 8

Talk about Logging in ASP.NET Core?

Accepted Answer

**Logging** is built-in and you get access to structured logs from the ASP.NET Core host itself to your application. With tools like [Serilog,](https://github.com/serilog/serilog-aspnetcore) you can extend your logging [easily](https://github.com/serilog/serilog-sinks-rollingfile) and save your logs to file, Azure, Amazon or any other output provider. You can configure verbosity and log levels via configuration (appsettings.json by default), and you can configure log levels by different categories.

Question 9

What is `ViewState`?

Accepted Answer

**View State** is the method to preserve the Value of the Page and Controls between round trips. It is a _Page-Level State Management_ technique. View State is turned on by default and normally serializes the data in every control on the page regardless of whether it is actually used during a post-back.  
  
A web application is stateless. That means that a new instance of a page is created every time when we make a request to the server to get the page and after the round trip our page has been lost immediately

Question 10

What exactly is an _application pool_? What is its purpose?

Accepted Answer

**Application pools** allow you to isolate your applications from one another, even if they are running on the same server. This way, if there is an error in one app, it won't take down other applications.

Additionally, applications pools allow you to separate different apps which require different levels of security.

Top 54 ASP.NET Interview Questions

What is ViewData?

What is the difference between ASP.NET and ASP.NET MVC?

What is Generic Host in .NET Core?

Talk about Logging in ASP.NET Core?

What is ASP.NET Core?

Can ASP.NET Core work with the .NET framework?

What is ViewState?

Explain startup process in ASP.NET Core?

What exactly is an application pool? What is its purpose?

What is a postback?

Explain Middleware in ASP.NET Core?

Explain the use of BackgroundService class in Asp.Net Core?

What is the correct pattern to implement long running background work in Asp.Net Core?

In OOP, what is the difference between the Repository Pattern and a Service Layer?

What are some benefits of using Options Pattern in ASP.NET Core?

How can you create your own Scope for a Scoped object in .NET?

What is ViewState? How is it encoded? Is it encrypted? Who uses ViewState?

List the events in ASP.NET page life cycle

Explain usage of Dependency Injection in ASP.NET Core

Where the viewstate is stored after the page postback?

What are the different validators in ASP.NET?

What exactly is the difference between .NET Core and ASP.NET Core?

What are the different types of caching?

In which event of page cycle is the ViewState available?

What is the difference between Server.Transfer and Response.Redirect?

What are the sub types of ActionResult?

What is the meaning of Unobtrusive JavaScript?

How can we prevent browser from caching an ASPX page?

What is new in ASP.NET Core 2, compared to ASP.NET Core 1?

Explain JSON Binding?

What is the difference between Hosted Services vs Windows Services?

What is the difference between Hosted Services vs WebJobs?

What is the difference between IHost vs IHostBuilder vs IHostedService?

What is the difference between classic and integrated pipeline mode in IIS7?

What is the difference between <system.web> and <system.webServer>?

What is an HttpHandler in ASP.NET? Why and how is it used?

When using DI in Controller shall I call IDisposable on any injected service?

What is the difference between ASP.NET Core Web (.NET Core) vs ASP.NET Core Web (.NET Framework)?

How we can force all the validation controls to run?

When to use Transient vs Scoped vs Singleton DI service lifetimes?

How to choose between ASP.NET 4.x and ASP.NET Core?

Is it possible to create web application with both WebForms and MVC?

What is the difference between web config and machine config?

What is Katana?

What is HttpModule in ASP.Net?

Which type if caching will be used if we want to cache the portion of a page instead of whole page?

What are the different types of cookies in ASP.NET?

What are the different Session State management options available in ASP.NET?

What is the equivalent of WebForms in ASP.NET Core?

What exactly is OWIN and what problems does it solve?

Are static class instances unique to a request or a server in ASP.NET?

Explain some deployment considerations for Hosted Services

What is Cross Page Posting?

Name some ASP.NET WebForms disadvantages over MVC?

What is `ViewData`?

What is `ViewState`?

Explain the use of `BackgroundService` class in Asp.Net Core?

In which event of page cycle is the `ViewState` available?

What is the difference between `Server.Transfer` and `Response.Redirect`?

What is the difference between `IHost` vs `IHostBuilder` vs `IHostedService`?

What is the difference between `<system.web>` and `<system.webServer>`?

What is an `HttpHandler` in ASP.NET? Why and how is it used?

When using DI in Controller shall I call `IDisposable` on any injected service?

What is `HttpModule` in ASP.Net?