Top 68 .NET Core Interview Questions And Answers

Question 1

What is the .NET Framework?

Accepted Answer

The .NET is a Framework, which is a collection of classes of reusable libraries given by Microsoft to be used in other .NET applications and to develop, build and deploy many types of applications on the Windows platform including the following:

*   Console Applications
*   Windows Forms Applications
*   Windows Presentation Foundation (WPF) Applications
*   Web Applications
*   Web Services
*   Windows Services
*   Services-oriented applications using Windows Communications Foundation (WCF)
*   Workflow-enabled applications using Windows Workflow Foundation(WF)

Question 2

What is .NET Core?

Accepted Answer

The .NET Core platform is a new .NET stack that is optimized for open source development and agile delivery on NuGet.

.NET Core has two major components. It includes a small runtime that is built from the same codebase as the .NET Framework CLR. The .NET Core runtime includes the same GC and JIT (RyuJIT), but doesn’t include features like Application Domains or Code Access Security. The runtime is delivered via NuGet, as part of the ASP.NET Core package.

.NET Core also includes the base class libraries. These libraries are largely the same code as the .NET Framework class libraries, but have been factored (removal of dependencies) to enable to ship a smaller set of libraries. These libraries are shipped as `System.*` NuGet packages on NuGet.org.

Question 3

What is the difference between `String` and `string` in C#?

Accepted Answer

`string` is an _alias_ in C# for `System.String`. So technically, there is no difference. It's like `int` vs. `System.Int32`.

As far as guidelines, it's generally recommended to use `string` any time you're referring to an object.
```csharp
string place = "world";
```

Likewise, it's generally recommended to use `String` if you need to refer specifically to the class.
```csharp
string greet = String.Format("Hello {0}!", place);
```

Question 4

What is .NET Standard?

Accepted Answer

The **.NET Standard** is a formal specification of .NET APIs that are intended to be available on all .NET implementations.

Question 5

What is _Boxing_ and _Unboxing_?

Accepted Answer

**Boxing** and **Unboxing** both are used for type conversion but have some difference:

* **Boxing** - Boxing is the process of converting a value type data type to the object or to any interface data type which is implemented by this value type. When the CLR boxes a value means when CLR is converting a value type to Object Type, it wraps the value inside a `System.Object` and stores it on the heap area in application domain.

* **Unboxing** - Unboxing is also a process which is used to extract the value type from the object or any implemented interface type. Boxing may be done implicitly, but unboxing have to be explicit by code.

The concept of boxing and unboxing underlines the C# unified view of the type system in which a value of any type can be treated as an object.

Question 6

What's the difference between _SDK_ and _Runtime_ in .NET Core?

Accepted Answer

* The SDK is all of the stuff that is needed/makes developing a .NET Core application easier, such as the CLI and a compiler.

* The runtime is the "virtual machine" that hosts/runs the application and abstracts all the interaction with the base operating system.

Question 7

Name some CLR services?

Accepted Answer

**CLR services**

*   Assembly Resolver
*   Assembly Loader
*   Type Checker
*   COM marshalled
*   Debug Manager
*   Thread Support
*   IL to Native compiler
*   Exception Manager
*   Garbage Collector

Question 8

What is the difference between `decimal`, `float` and `double` in .NET?

Accepted Answer

Precision is the main difference.

* **Float** - 7 digits (32 bit)
* **Double** -15-16 digits (64 bit)
* **Decimal** -28-29 significant digits (128 bit)

As for what to use when:

* For values which are "naturally exact decimals" it's good to use **decimal**. This is usually suitable for any concepts invented by humans: financial values are the most obvious example, but there are others too. Consider the score given to divers or ice skaters, for example.

* For values which are more artefacts of nature which can't really be measured exactly anyway, **float/double** are more appropriate. For example, scientific data would usually be represented in this form. Here, the original values won't be "decimally accurate" to start with, so it's not important for the expected results to maintain the "decimal accuracy". Floating binary point types are much faster to work with than decimals.

Question 9

What is the difference between .NET Core and Mono?

Accepted Answer

To be simple:
* Mono is third party implementation of .Net Framework for Linux/Android/iOs
* .Net Core is Microsoft's own implementation for same.

Question 10

What are some characteristics of .NET Core?

Accepted Answer

* **Flexible deployment**: Can be included in your app or installed side-by-side user- or machine-wide.

* **Cross-platform**: Runs on Windows, macOS and Linux; can be ported to other OSes. The supported Operating Systems (OS), CPUs and application scenarios will grow over time, provided by Microsoft, other companies, and individuals.

* **Command-line tools**: All product scenarios can be exercised at the command-line.

* **Compatible**: .NET Core is compatible with .NET Framework, Xamarin and Mono, via the .NET Standard Library.

* **Open source**: The .NET Core platform is open source, using MIT and Apache 2 licenses. Documentation is licensed under CC-BY. .NET Core is a .NET Foundation project.

* **Supported by Microsoft**: .NET Core is supported by Microsoft, per .NET Core Support

Top 68 .NET Core Interview Questions

What is the .NET Framework?

What is .NET Core?

What is .NET Standard?

What is the difference between String and string in C#?

What is Boxing and Unboxing?

What is Generic Host in .NET Core?

What is IoC (DI) Container?

What is CLR?

What is an unmanaged resource in .NET?

What is a .NET application domain?

What is CTS?

What is .NET Standard and why we need to consider it?

What is MSIL?

Name some CLR services?

What's the difference between SDK and Runtime in .NET Core?

What are some characteristics of .NET Core?

What you understand by Value types and Reference types in .NET? Provide some comparison.

What is the difference between decimal, float and double in .NET?

What is the difference between .NET Core and Mono?

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

What is the difference between .NET Standard and PCL (Portable Class Libraries)?

Explain two types of deployment for .NET Core applications

What officially replaces WCF in .Net Core?

What is Explicit Compilation?

What are the benefits of Explicit Compilation (AOT)?

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

What is the difference between Class Library (.NET Standard) and Class Library (.NET Core)?

What's is BCL?

What is JIT compiler?

When should we use .NET Core and .NET Standard Class Library project types?

Explain the IoC (DI) Container service lifetimes?

What is FCL?

What about MVC in .NET Core?

What does Common Language Specification (CLS) mean?

What is difference between .NET Core and .NET Framework?

What's the difference between .NET Core, .NET Framework, and Xamarin?

What is Kestrel?

Is there a way to catch multiple exceptions at once and without code duplication?

What is the use of the IDisposable interface?

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?

Explain the difference between Task and Thread in .NET

Explain the difference between Managed and Unmanaged code in .NET?

Explain what is included in .NET Core?

What is CoreCLR?

What's the difference between gRPC and WCF?

Explain different types of Inheritance

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

What is the difference between IHost vs IHostBuilder vs IHostedService?

What is the difference between Hosted Services vs Windows Services?

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

Why shouldn't I use the Repository Pattern with Entity Framework?

How to choose the target version of .NET Standard library?

Does .NET support Multiple Inheritance?

Explain Implicit Compilation process

What is the difference between .NET Framework/Core and .NET Standard Class Library project types?

What are benefits of using JIT?

Why does .NET use a JIT compiler instead of just compiling the code once on the target machine?

Explain how does Asynchronous tasks Async/Await work in .NET?

Why does .NET Standard library exist?

What is the difference between CIL and MSIL (IL)?

What's the difference between RyuJIT and Roslyn?

What is the difference between AppDomain, Assembly, Process and a Thread?

Could you name the difference between .Net Core, Portable, Standard, Compact, UWP, and PCL?

What is the difference between Node.js async model and async/await in .NET?

Explain when to use Finalize vs Dispose?

Explain some deployment considerations for Hosted Services

How many types of JIT Compilations do you know?

What is the difference between `String` and `string` in C#?

What is the difference between `decimal`, `float` and `double` in .NET?

What is the use of the `IDisposable` interface?

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

Explain the difference between `Task` and `Thread` in .NET

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

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

Explain how does Asynchronous tasks `Async/Await` work in .NET?

What is the difference between `AppDomain`, `Assembly`, `Process` and a `Thread`?

What is the difference between Node.js async model and `async/await` in .NET?

Explain when to use `Finalize` vs `Dispose`?