Top 66 Senior .NET Developer Interview Questions & Answers 

.Net, is a widely used framework for developing Windows applications and encompasses languages such as C#, Cobol, Perl, VB.Net, etc. Are you looking for a job in this domain? Here is a list of expected .NET core interview questions and answers to help you get through your next interview. Let’s go for it:

1. What is the .Net framework, and how does it work?

It is a virtual machine that executes a managed code. The code is compiled from C# or VB .NET and is executed by the CLR (Common Language Runtime).

Its working is as follows:

• You create a program in C # or VB.Net and compile it. The code is then translated to CIL (Common Intermediate Language).
• The program is assembled into bytecode to generate a CLI (Common Language Infrastructure) assembly file of.exe or .dll format.
• When you run the program (or the DLL), it is executed by the .Net framework CLR (Common Language Runtime). Since the code isn’t directly run by the operating system, it is called “Managed Code“.
• The .Net Framework CLR, through the JIT (Just-In-Time) Compiler, is responsible for compiling this code managed in the intermediate language. The compiled code is then sent to the native machine language assembler for the CPU to execute it.

The CIL (Common Intermediate Language) is the language that understands the.Net Framework.

• C # and VB .Net are languages that we understand as humans.
• C # and VB .Net are translated to CIL.

Take care to remember the details. It may look like basic information, but it is among recruiters’ top senior .NET developer interview questions.

2. What are some of the key components of .NET?

Although .NET is made upon several essential components, some are more common than others based on the frequency of use. Following is a list of key .NET components you must know about:

• CLR (Common Language Runtime)
• .NET Framework
• .NET Library
• Application Domain
• Garbage Collector
• JIT Compiler

3. What are EXE and DLL?

1. EXE and DLL are both assembly executable modules with different capabilities.
2. EXE is an extension for executable files that run the application for which they are developed. It defines an entry point and can run independently; however, its use is restricted to the originally designed application. Additionally, EXE always establishes a separate memory space unique to the application.
3. DLL, in contrast, is an extension for a dynamic link library and an essential component for shared libraries. Unlike EXE, DLL can be used by other applications and does not define an entry point. Since the DLL extension is used for shared libraries, it leverages the space of the calling application.

This is an example of one of the most basic senior .NET developer interview questions, so keep the answer in mind.

4.What is a dynamic type in .NET?

Dynamic type is the opposite of static type and it is used to avoid compile-time type checking. Although it is a static type by nature, an object of dynamic type can bypass static type checking. Hence, instead of checking the type of the dynamic type variable at compile-time, the compiler checks it at run time.

5.What is MSIL?

Microsoft Intermediate Language (MSIL) is a type of Common Intermediate Language. At its base, it’s a set of instructions that can be converted to native code without CPU intervention. It is made of instructions for memory handling, storing and initializing values, calling methods, etc.

Typically, a CLR’s JIT compiler converts the MSIL code to native code during runtime.

6.What is Common Language Specification?

Common language specification (CLS) is a subset of Common Type System. Its common language features help develop .NET compatible applications and services because they can communicate with objects designed using different languages.

Hence, CLS acts as a common ground for components, helping them fit together without disruption despite their diverse base languages.

7.What is Heap, and what is Stack?

• Both are memory locations, wherein Heap is global, and Stack is local.
• The Heap is application-level, while the Stack is thread-level.
• The Stack has a defined first-in-first-out stack structure, while the Heap does not have a defined data structure.
• Its size is defined at the time of its creation. For Heap, the size is defined when starting the application, and for Stack, when creating a thread.
• Both can grow dynamically.
• The Stack is faster than the Heap. A stack is in “cache” and doesn’t have to synchronize with other threads like the Heap.
• The Stack stores values while the Heap stores objects.

8.What is a Garbage Collector?

A Garbage Collector is an automatic process of memory release. When memory goes low, it goes through the Heap and eliminates the objects no longer in use. It frees up memory, reorganizes remaining threads, and adjusts pointers to these objects, both in Heap and Stack.

9.What are the three generations of garbage collection?

As mentioned above, the Garbage Collector helps free up memory space by disposing of unused objects when memory becomes low. The memory head a garbage collector typically deals with is categorized into three generations:

• Generation 0: This generation contains the newest or most short-lived objects. They are collected fairly frequently and efficiently.
• Generation 1: Contains objects that have been present long enough to be marked for collection but have not been collected due to sufficient heap space. They are removed less frequently than Generation 0, and the process is less efficient.
• Generation 2: Contains objects that have remained in memory for the longest period. Collection for Generation 2 objects happens even less frequently than Generation 1, with the ideal ratio for 1 and 2 being 10:1.

10.What is a delegate?

It is the definition of a method that encapsulates certain arguments and types of return. It allows passing a method as an argument of a function, as long as it matches its specific signature.

11.What is CTS?

Common Type System or CTS is a standard that specifies how types are represented and managed in common language runtime. It provides the core support for cross-language integration, making it essential for application development.

• There are a few key roles a CTS performs in a .NET framework:
• Define common rules for all languages to follow to ensure they can interact when used in a single application.
• Create a framework to support cross-language integration in code execution.
• Develop a model for implementation of multiple programming languages in addition to creating a library with primitive data types.

12.What is LINQ?

It is standardization to consult data and convert it into objects, regardless of the source. It is a query manager for databases, XML, and enumerable collections using a single language.

13.How does LINQ work?

Internally build the correct query (in the case of databases) or generate the corresponding operations on the collections or parse the XML and returns the relevant data. It encapsulates all these behaviors and provides a single implementation. In this way, we can use the same queries, the same language, independently of the underlying data source.

14.What are the deferred execution and the immediate execution in LINQ?

A deferred execution encapsulates a query’s definition without executing it till the data is used at runtime. However, an immediate implementation calls the query at the same moment of its definition.

By default, the executions are deferred, but we can do them immediately by calling “ToList ()”. For example, in this way, a list of objects will be executed and returned to us when we define it.

15.What are an object and a class?

An object is an instance of a class, and a class is a template for creating objects.

Class is the definition of an object, the description of its characteristics and operations, its properties, and its methods. An object has an identity because its characteristics have values.

16.What are inheritance, polymorphism, and encapsulation?

Inheritance is the ability to reuse definitions from one class to another and base one class on another.

Polymorphism helps declare the same method within a class with different arguments or return types.

Encapsulation is to be able to expose only the methods, property, and arguments necessary to use the operations of a class. However, the detailed implementation remains private, hidden to other objects.

17.What is an attribute and how are they used?

An attribute is a declarative tag or a powerful method of associating metadata with code. Hence, its primary function is to convey information about program assemblies, classes, methods, structures, etc. to runtime.

They add metadata to a program and you can apply several attributes to program elements like assemblies, modules, etc.

18.What is Metadata?

Metadata is information or data structures about the types defined in a program. It is machine-readable information that may contain basic details like size, format, etc. 

19.What is the difference between an abstract class and an interface?

• An abstract class can contain both public and private constructors, methods, and fields. On the contrary, the interface contains only methods and public properties.
• You can only inherit from an abstract class but implement many interfaces.
• An interface defines behavior, something that the class that implements it can do. Contrary, an abstract class defines what the class is and what it represents.
• You can’t instantiate anyone.
• An abstract class is useful when creating components, making a partial initial implementation and a specific definition. This leaves you free to implement other methods.

Senior .NET developer interview questions about this topic take on various formats, so strengthen conceptual understanding. It will help you know the answer irrespective of the framing of the question.

20.What is the Single Responsibility Principle?

Single Responsibility refers to a class performing a specific function or responsibility instead of leaning towards high cohesion.

High cohesion is when one class performs multiple responsibilities.

21What is God Class?

A God class is a class that controls too many functions or objects in the system. Typically a class is not supposed to control several objects; hence such a class is outside the parameters of logic and becomes ‘the class that controls everything.’

22.What is the difference between public, static, and void?

Public declared variables or methods are accessible anywhere in the application.

Static declared variables or methods are globally accessible without creating an instance of the class. A static member is by default not globally accessible; it depends upon the type of access modified used. The compiler stores the address of the method as the entry point and uses this information to begin execution before any objects are created.

A Void is a type modifier that states that the method or variable does not return any value.

23.What is a sealed class?

It is a class that is not inheritable. A sealed class comes into use for a super-specialized class by design and prevents modification by overwriting.

24.What is a “jagged array”?

The Array, which has elements of type array, is called a jagged Array. The elements can be of different dimensions and sizes. We can also call a jagged Array an Array of arrays.

25.What is serialization?

Serialization converts an object to a data stream. However, for this, you must implement ISerialize.

26.What is the difference between constants and read-only variables?

For constants, the compilation contains declaration and initialization. Its value cannot change.

Read-only is only used when we want to assign the value at run time.

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

A ‘Thread’ is a unit of CPU utilization, hence, it is an OS-level instruction and offers extensive control to the programmer. It has a dedicated program and memory area, and you can use it to Abort, Suspend and Resume other threads. Threads are built into the operating system instead of being a .NET construct.

Conversely, ‘Tasks’ are loaded in memory and do not create their OS thread. They are not independent, unlike threads, and need a scheduler for execution. Another key feature of Task is that you can track its finishing time.

28.What is Multithreading?

Multithreading is a process that uses multiple threads, each of which performs unique activities. In this way, one process can perform several types of activities at the same time. You can see the number of threads a single process is running in the Task Manager on your PC.

Following are the ways in which .NET supports multithreading:

1. Using ThreadPool class with asynchronous methods.
2.   Starting threads with ThreadStart delegates.

29.Explain the differences between preemptive threads and non-preemptive threads.

A preemptive threading model is flexible and allows the virtual machine to intervene to change control of threads when it sees fit. In contrast, in a non-preemptive threading model, a thread continues to exercise control until it is blocked or explicitly yields control.

30.What is a Let clause?

Let clause is part of a query syntax or query expression that introduces a variable that you can initialize with the result of your preferred expression. This variable can be used at other points in the query to invoke the programmed expressions.

31.Explain Mutex

Threads share a mutually exclusive resource manager, Mutex. It ensures that only one thread at a time makes use of one resource (one object) at a time. It is like a moderator that controls the microphone and gives the word to one person at a time. Thus, Mutex grants access to resources one thread at a time. For this, it puts the threads that want to access resources “on hold” until those are in use.

Mutex is a popular topic for senior .NET developer interview questions, especially because of its applications.