20 .NET Developer Interview Questions and Answers for 2024

You are on this page since you need to hire .NET developers, and you need .NET developer interview questions. Since .NET is the most popular framework in its category, .NET developers are in great demand. Not just .NET interview questions but you also need to understand the hiring process. You are certainly on the right page since we first explain the hiring process and then share comprehensive interview questions and answers.

Publish an effective and persuasive .NET job advertisement

It can take significant effort to attract competent .NET developers to your organization. Create and publish an effective job ad toward this, and cover the following:

Company descriptions

Clearly, you need to describe your company based on hard facts. At the same time, introduce your organization in an exciting manner to attract top programmers.

Elaborate on the growth trajectory of your company since competent developers want to work in successful organizations. Talk about the work environment and organizational culture. Stress on having an innovation-focused culture with high employee engagement. Today’s high-performing developers value such a culture.

Describe the compensation and benefits policies with an underlying message of rewarding performers. Explain the all-round professional development opportunities in your organization.

Job descriptions for .NET developers

You will surely describe the commonly-known job descriptions of .NET developers, e.g., developing, maintaining, and enhancing .NET applications. In addition to that, explain why the .NET developer role is important to your organization.

Elaborate on the significance of the project including any strategic reasons. You see, the developers reading your job ad should feel that you have an important project at hand. Smart developers know that delivering strategic projects successfully brings considerable growth opportunities to them.

.NET developer roles and responsibilities

Your job ad should surely include the standard roles and responsibilities of a .NET developer. However, you also need to stimulate the adventurous person in the developer checking out your job ad.

Cover the well-known roles and responsibilities of .NET developers, e.g.:

• The developer should carefully study and analyze the requirements and technical solutions of the project.
• Developers need to create quality .NET-based web applications.
• .NET developers should take an active part in testing and deployment.
• Programmers should adhere to all relevant software development processes, methods, standards, and best practices.
• Developers should maintain and enhance existing .NET applications.
• .NET developers should provide the relevant status reports.
• Programmers should meaningfully participate in innovative initiatives.

Emphasize high-visibility tasks requiring in-depth skills, which will convince developers about growth opportunities in your organization. After all, developers know that they grow when they utilize innovative opportunities and solve critical challenges.

.NET framework and other relevant skills

You would like .NET developers with good fundamental knowledge of software development. Therefore, you would want them to have a bachelor’s degree in computer science, information technology, or related disciplines. Mention that in the job ad and specify the following skill requirements:

• Developers need comprehensive knowledge of the .NET web development framework.
• .NET developers need the experience of developing web applications and web services from the beginning to the end using the .NET technology.
• Software engineers should have good knowledge of developing web pages and websites using ASP.NET.
• Programmers should have a thorough knowledge of C# and VB.NET (Visual Basic .NET). You need to specify if you need developers with skills in other programming languages.
• .NET developers need in-depth skills in the .NET platform and important tools like Visual Studio.
• Software engineers should have good knowledge of using .NET core to develop cross-platform cloud applications. If you need developers with skills in the Mono framework, please specify that.
• Developers need a sound knowledge of object-oriented programming (OOP).
• .NET developers should have excellent knowledge of SQL databases like MS SQL Server, MySQL, PostgreSQL, etc. If you plan to use a NoSQL database like MongoDB or Apache Cassandra for developing .NET applications, write that in the skill requirements.
• Programmers should have sound knowledge of architectural patterns like MVC (Model View Controller).
• .NET developers need a good understanding of user interface (UI) design.
• Developers must have proficiency with version control tools like Git.
• .NET programmers need excellent knowledge of software development processes, methods, tools, and best practices.
• Software engineers need a sound knowledge of testing and DevOps.
• Developers should have soft skills like communication skills, problem-solving skills, teamwork, empathy, and the ability to see the bigger picture.

.NET interview questions and answers for hiring junior developers

Can you execute your .NET application development project with junior developers? Use the following interview questions to assess their skills:

1. Tell me which one is preferable between an “.EXE” file and a “.DLL” file for my large-scale .NET application development project.

You should use a “.DLL” (Dynamic Link Library) file while executing your large-scale .NET application development project. You will likely need to reuse code multiple times in a large .NET project. A “.DLL” file can have reusable code. You can reference and use a “.DLL” file in multiple applications.

On the other hand, an “.EXE” file is the executable file for a standalone program. You can’t reuse code.

2. Should I use the Code Access Security (CAS) feature of .NET in my current project?

You can no longer use Code Access Security (CAS) on .NET 6+. The .NET framework project team has removed this feature due to the complexities of implementing CAS.

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Remember that CAS was to protect system resources like event logs, network, user interface, local drives, and directories from malicious code. CAS didn’t protect a software application from malicious users.

Therefore, you will not need to use CAS to ensure application security. Use operating system capabilities like user accounts, containers, and virtualization to protect your system resources.

3. Write a LINQ (Language Integrated Query) query used in C# to select a particular value from a string of values.

We first create a string in C#. The following is an example:

“

// string as a collection of values

IList<string> stringList = new List<string>() {

“FOOTBALL PLAYERS”,

“STUDENT INTERNS”,

“PHYSICS LECTURERS”,

“MATHS PROFESSORS”

};

“

Then, we write a LINQ query to pick the item containing the value “INTERNS”.

“

// LINQ Query To Pick One Particular Value

var result = from s in stringList

where s.Contains(“INTERNS”)

select s;

“

4. Describe the steps to include a NuGet in .NET framework applications using Visual Studio on Windows.

We need to do the following:

• First, we need to navigate to our project and select “Artifacts”. We should then select our feed.
• Subsequently, we should select “Connect to feed”.
• We now need to select “Visual Studio” from the navigation panel on the left.
• At this point, we should copy the “Source” URL.
• We must set up Visual Studio on our Windows computer. After opening Visual Studio, we should select “Tools > Options”.
• We need to select “NuGet Package Manager”. Subsequently, we should select the “Package Sources”.
• We need to enter the name of our feed and the source URL copied earlier.
• Subsequently, we should use the option to add a new package source.
• We need to clear the checkbox named “nuget.org” if we have enabled upstream sources in our feed.
• After clicking “OK”, we need to open Visual Studio.
• We should use the “Solution Explorer” and select “Manage NuGet Packages”.
• After we browse, then we need to select the feed from the “Package source” dropdown menu.
• We should now search for the packages.
• Subsequently, we need to navigate to NuGet.org to find the package of our choice.
• From the “Package Manager”, we need to copy the Install-Package command.
• Now, we need to open Visual Studio. We should select “Tools > NuGet Package Manager > Package Manager Console”, which opens the “Package Manager Console”.
• We should enter the install command we had copied earlier into the “Package Manager Console”.

5. In VB.NET “For Next Loop” syntax, what are the roles of the “start” and “end” parameters?

The “start” parameter is the initial value of the “variable name” in a VB.NET “For Next Loop”. On the other hand, the “end” parameter is the final value.

Before one iteration completes, VB.NET compares the current value of the variable with the “end” parameter value. It continues to iterate if the current value is less than the “end” parameter value. If the value of the “variable name” exceeds the “end” parameter value, then VB.NET completes the loop.

6. Explain how you will create a class without inheritance in a C#/.NET project.

Since all classes created in a C#/.NET project will support inheritance by default, we need to explicitly make a class without inheritance. We should use the “sealed” keyword to create a class that doesn’t allow inheritance.

The syntax of using the “sealed” keyword is as follows:

“

sealed class Science

{

…

}

“

Now, you can’t create another class and try to make it inherit the sealed class. Take the example of another class named “Physics”. The following code will not work:

“

class Physics : Science

{

…

}

“

You will receive an error message that reads as follows:

“

‘Physics’: cannot derive from sealed type ‘Science’

“

7. In my C#/.NET project, I want to convert a value type to a type object. Subsequently, I want to extract the value from the type object. Write code to accomplish this.

We need to use the “boxing” and “unboxing” processes for this requirement. By using the “boxing” process, we can convert a value type to a type object. On the other hand, the “unboxing” process enables us to extract the value from that object.

The following code snippet in the C# programming language shows an example of this:

“

int m = 25;

object exampleObject = m;   // This is the boxing process

m = (int)exampleObject;       //  This is the unboxing process

“

.NET developer Interview questions and answers for hiring mid-level developers

If you need to hire mid-level .NET developers, then use the following interview questions:

1. Explain how the .NET garbage collector deals with large objects.

The .NET garbage collector uses 3 generations for the garbage collection process, which are as follows:

• Generation 0: It’s the youngest generation of objects, and this category has short-lived objects. The .NET garbage collector operates most frequently for this generation. It reclaims memory for most objects during this process. Only the objects that remain after this generation go on to the next generations.
• Generation 1: While this generation also has short-lived objects, the .NET garbage collection uses this as a sort of “middle path”. If the garbage collector can’t free up enough memory for the application after a generation 0 garbage collection, then it uses generation 1.
• Generation 2: The .NET garbage collector operates for this generation only after it has acted on the generation 0 and generation 1 objects. This generation covers long-lived objects only.

Now, the .NET garbage collector treats the large objects differently. It categorizes them as “Generation 3”, however, these are really Generation 0 objects. The garbage collector sends these objects to the “Large Object Heap” (LOH) and performs garbage collection as a part of generation 2 operations.

2. In an ADO.NET connection pool, I want to add a maximum of 200 connections. How can I achieve this?

We need to use the “Max Pool Size” parameter, which is one of the parameters to control connection pooling behaviors. You have to specify the maximum pool size of 200 in this parameter. If you don’t specify, then ADO.NET will use the default value of 100 for this parameter.

You need to use the “ConnectionString” property to set the value for this parameter. The following is an example of the code:

“

connection.ConnectionString = demosqlConnectString + “Connection Timeout=20;Connection Lifetime=0;Min Pool Size=0;Max Pool Size=200;Pooling=true;”;

“

3. In my VB.NET project, I want to use Multiple Document Interface (MDI) forms. First, I want to set a parent form to a child form. Subsequently, I want to arrange the child form in the parent form. How can you do this?

For the first requirement, we need to use the MdiParent property of MDI forms. It sets a parent form to a child form.

For the second requirement, we need to the LayoutMdi() method for MDI forms. This method allows us to arrange a child form in the main form or parent form.

4. Among .NET compatible languages, which one do you prefer most? State the reasons.

I prefer C#, due to the following reasons:

• C# is one of the multiple programming languages for which you can avail of managed code. Managed code offers many advantages to developers. It takes care of many aspects without much effort from developers, e.g., better security, prevention of memory buffer overflow, garbage collection, exception handling, easier debugging, etc.
• A powerful language, C# is popular with many developers.
• Programmers who have used C and C++ prefer C# for its modern capabilities.
• C# offers excellent scalability and performance.

Other programming languages supported by .NET are also good. Many of these programming languages are very popular due to their powerful features and all-round utilities. The following are a few examples:

• Visual Basic (VB);
• C++;
• C#;
• Perl through Active Perl;
• F#;
• Ada;
• IronPython;
• IronRuby;
• Jscript;
• PHP through Phalanger;
• Visual COBOL.NET.

5. My planned .NET application will have extensive string manipulations. Should I use “String” or “StringBuilder”? State the reasons for your recommendation.

You should use “StringBuilder”. Since StringBuilder is mutable, you can modify a StringBuilder object. In effect, you are changing the existing object, and you aren’t creating a new object. When you have a lot of string manipulations, this results in more efficient program execution.

However, “String” is immutable. You can’t change the value of a String object. A new string object gets created every time you need to modify a string. This overhead causes inefficient program execution when there’s plenty of string manipulation.

6. In an ASP.NET project, how will you take care of the final clean-up work for a page?

We should use the ASP.NET page life cycle event named “unload” for the final clean-up work for a page. This even takes care of all the relevant clean-up works, e.g.:

• Closing open files;
• Closing database connections;
• Completing the logging activities;
• Request-specific tasks.

At this stage of the page life cycle, the rendering of the page and its controls was already complete. We should be careful so that we don’t make any more changes to the response stream. ASP.NET shows an exception error if we invoke methods like “Response.Write” for the same page at this stage.

7. I want to use MySQL on my ASP.NET project. I plan to create stored procedures and modify them. Tell me how I can accomplish this.

If you must use MySQL on your ASP.NET project, then you can’t modify an existing stored procedure.

You need to drop the procedure first using the DROP PROCEDURE statement. The syntax for this statement is as follows:

“

DROP PROCEDURE spSTOREDPROCEDURENAME;

“

Subsequently, you need to create a new stored procedure to incorporate your changed requirements. Use the CREATE PROCEDURE statement for this. The following is the syntax for this statement.

“

CREATE PROCEDURE spNEWSTOREDPROCNAME;

“

Can you use MS SQL Server in place of MySQL? Then, you can modify a stored procedure with the help of the “ALTER PROCEDURE” statement.

Senior .NET app developer interview questions and answers

You can use the following questions to evaluate the relevant expertise of senior .NET developers:

1. Are there classes in the .NET class library that don’t comply with the Common Language Specification (CLS)? Does this non-compliance have any impact?

There are classes in the .NET class library that aren’t CLS-compliant. These are as follows:

• SByte: It’s an 8-bit unsigned integer.
• UInt16: This is a 16-bit unsigned integer.
• UInt32: UInt32 is a 32-bit unsigned integer.
• UInt64: It’s a 64-bit unsigned integer.
• UIntPtr: For this unsigned integer, the size depends on the operating system of the platform.

CLS-non-compliance can have impacts on interoperability. For example, while C# can use “UInt” classes, VB might have challenges with them.

2. What should I watch out for when dealing with the heap in my .Net project?

Stack and Heap help .NET applications with memory management, and you should indeed keep certain aspects in mind when dealing with the heap. Unlike Stack, which keeps track of the program execution, heap tracks the more precise objects. Heap is used for dynamic memory allocation too.

Stack handles its memory management. However, the heap depends on garbage collection to clean up the unused code objects. You need to ensure that the garbage collection happens effectively when dealing with the heap.

3. In my C#/.NET project, I want to use a delegate object with the return-type as an integer to call a method with the return-type as a character. Explain how I can do this.

You can’t accomplish this task. A delegate object in C# has a signature and return-type. These delegate objects can only call methods with the same return-type and signature. Since your requirements involve different return-types between the delegate object and method, the delegate object can’t call the method that you want.

4. Read the following Multipurpose Internet Mail Extensions (MIME) message with multiple segments. State the type of content that will be used by default for the 2nd segment (the placeholder text in red). State the reason for your answer.

Code snippet  

“

POST echo/post/form HTTP/1.1

Host: Microsoft.Com

Content-Type: multipart/form-data; boundary=–234

Content-Length: 256

–234

Content-Disposition: form-data; name=”file2″; filename=”image.png”

Content-Type: image/png

[image.png file contents]

–234

Content-Disposition: form-data; name=”unknownsegment”

WHAT SHOULD BE USED HERE BY DEFAULT?

–234

Content-Disposition: form-data; name=”file1″; filename=”readme.txt”

Content-Type: text/plain

[readme.txt file contents]

–234

“

Answer:

The 2nd segment in this multi-part MIME message will use “text/plain” by default. That’s because the above code snippet doesn’t show any content-type for the message in that segment. MIME messages consider “text/plain” by default when the content-type is unspecified.

5. What do you think is the top application security risk for me to mitigate in a .NET development project? Suggest mitigation measures.

The .NET security architecture is robust with powerful solutions. However, you must always proactively mitigate application security risks. You should consider broken access control as the topmost application security risk in a .NET development project.

Consider the following mitigation measures:

     1. Implement robust account management

Do the following:

• Make sure that cookies are sent with HttpOnly flag. That prevents scripts from the client-side from accessing cookies.
• Reduce session timeout and eliminate sliding expiration. You can then reduce the time duration for which a hacker can steal a session.
• Enforce the sending of cookies over HTTPS.
• Secure login, password reset, and account registration functions from brute force attacks. Use techniques like throttling.

     2. Implement function-level access control

Implement this at the controller or method level.

     3. Secure all direct object references

Make sure that users only access objects that they should access.

6. I am using PLINQ in my C#/.NET project. I have coded the following query shown in the code snippet. Will it deliver efficient query execution? State with reasons.

Code Snippet

“

var q = from student in students.AsParallel()

from grade in student.Grades.AsParallel()

where grade.MathsScore > 50

select new { student, grade };

“

Answer

You are at risk of over-parallelization, which can degrade the query performance. You should only parallelize the outer data source (students).

You can make an exception to the above recommendation if you have any of the following situations:

• You have a very long inner data source. Check if “student.Grades” in this case is a very long data source.
• There are expensive computational operations on each grade.
• You know that the target system has enough processors needed to manage the threads created by parallelizing the query on “student.Grades”.

Hiring .NET developers?

You will likely find this hiring guide and the set of .NET framework interview questions helpful. However, you still need to invest significant time and effort to hire competent Net developers. That’s even more the case when hiring freelancers.

However, we at DevTeam.Space can help. We have many full-time .NET developers with excellent skills, extensive experience, and a high degree of motivation. Our rigorous vetting process ensures that you get only quality developers. Your interview efforts reduce considerably when you hire .NET software engineers from us.

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