Interviewing for a developer position can be challenging, but being prepared with the right questions can make all the difference. Here’s a comprehensive list of useful interview questions to help you prepare for your next technical interview.
Q1) Please introduce yourself.
Answer: I am [Your Name], currently working as a [Your Current Position] with [Your Company/Organization]. I have [Number] years of experience in [Your Field], specializing in [Your Area of Expertise]. I completed my [Your Degree] in [Your Major] from [Your University/College].
Q2) What kind of security mechanism do you use for securing web APIs?
Answer: I use various security mechanisms such as HTTPS/TLS for secure communication, OAuth 2.0 with JWT (JSON Web Tokens) for authentication and authorization, CORS policies to restrict cross-origin requests, and rate limiting to prevent abuse.
Q3) How does OAuth work?
Answer: OAuth is an open-standard authorization protocol that allows applications to gain limited access to user accounts on an HTTP service. It works by enabling secure delegated access and authorization without exposing user credentials.
Q4) Is there any expiration mechanism for the token?
Answer: Yes, tokens issued through OAuth typically have an expiration time (expires_in) after which they are no longer valid. This helps mitigate security risks associated with long-lived tokens.
Q5) Have you used the refresh token mechanism?
Answer: Yes, refresh tokens are used in OAuth flows to obtain new access tokens without prompting the user to re-enter their credentials. They help maintain persistent authentication sessions.
Q6) What are different state management techniques in ASP .NET?
Answer: ASP.NET offers various state management techniques including in-process (Session state, Application state), out-of-process (StateServer and SQLServer), and client-side (Cookies, Query strings, Hidden fields).
Q7) What is in-proc session management?
Answer: In-process session management stores session data within the ASP.NET worker process memory. It's fast but can lead to scalability issues in web farms or during application restarts.
Q8) What are different options to store session data in ASP.NET?
Answer: Session data in ASP.NET can be stored in-process (default), StateServer (out-of-process), SQLServer (out-of-process), or using custom session providers.
Q9) What are the steps to store session data in SQL Server?
Answer: To store session data in SQL Server, configure the session state mode to SQLServer in web.config, provide a connection string to the SQL Server database, and ensure the session state database schema is installed using aspnet_regsql.exe.
Q10) Have you hosted applications in the cloud?
Answer: Yes, I have experience deploying applications to cloud platforms like Microsoft Azure, AWS, and Google Cloud Platform. I utilize cloud services for scalability, reliability, and ease of maintenance.
Q11) What is an application pool?
Answer: An application pool in IIS (Internet Information Services) is a set of one or more web applications that share a common configuration and worker process. It provides isolation, resource management, and improved application reliability.
Q12) What is an out of memory exception? How will you handle this?
Answer: An out of memory exception occurs when an application attempts to allocate memory but fails due to insufficient available memory. Handling involves optimizing memory usage, identifying memory leaks, and implementing robust error handling and logging.
Q13) Sometimes there are cases where you need to store data such as reports in session. How will you clear data of one report in session if you move to another?
Answer: To clear data of one report stored in session when navigating to another, I would explicitly remove or invalidate the session variables associated with the previous report. This ensures efficient memory usage and prevents data inconsistencies.
Q14) How do you store a data table in view state? What if the data table has millions of records?
Answer: Storing a data table in view state involves serializing the data table object into a string and assigning it to the ViewState["key"]. For large data tables, it's recommended to consider alternative storage solutions such as caching or retrieving data on demand to avoid performance issues.
Q15) What are ref and out parameters?
Answer: ref and out are keywords used in C# to pass arguments to methods by reference instead of by value. ref parameters must be initialized before they are passed to a method, whereas out parameters are typically used for returning values from methods.
Q16) What is the finally block? When will it execute?
Answer: The finally block in C# is used in exception handling to specify code that should always execute, regardless of whether an exception occurs or not. It executes after try and catch blocks, or after the try block if no exceptions are thrown.
Q17) Can you explain access modifiers?
Answer: Access modifiers (e.g., public, private, protected, internal, protected internal) control the visibility and accessibility of classes, methods, and properties in C#. They enforce encapsulation, data hiding, and code security within applications.
Q18) What is a design pattern? Have you used any in your application?
Answer: Design patterns are reusable solutions to common software design problems. Examples include Singleton, Factory, and MVC (Model-View-Controller). I have implemented design patterns like Singleton for managing global resources and MVC for structuring web applications.
Q19) Can you describe the dependency injection pattern?
Answer: Dependency Injection (DI) is a software design pattern used to implement Inversion of Control (IoC) by injecting dependencies into a class rather than the class creating them. It enhances modularity, testability, and maintainability of applications.
Q20) Which domain are you working in?
Answer: I am currently working in [Your Domain/Industry], focusing on [Specific Projects or Technologies]. This includes [Brief Description of Your Responsibilities or Projects].
Q21) Do you have healthcare experience?
Answer: Yes, I have experience working on healthcare-related projects, ensuring compliance with regulations such as HIPAA (Health Insurance Portability and Accountability Act). This involves handling sensitive patient data securely and implementing robust data protection measures.
Q22) Have you worked with LINQ?
Answer: LINQ (Language-Integrated Query) is a powerful feature in C# used for querying and manipulating data. I have utilized LINQ to SQL for database queries and LINQ to Objects for in-memory data manipulation in various projects.
Q23) What is lazy loading in LINQ?
Answer: Lazy loading in LINQ defers the loading of related objects or data until the point where they are actually needed. This optimization technique improves performance by loading data only when required, reducing unnecessary database queries.
Q24) You have used global and local temp variables. What is the difference? Which do you use when?
Answer: Global variables are accessible throughout the entire program, whereas local variables are limited to the scope in which they are defined (like within a function or a block). When to use: Use global variables when you need data to be accessible across multiple functions or modules. Use local variables when you only need data within a specific function or block and want to avoid unintended side effects or variable name conflicts.
Q25) What are magic tables?
Answer: Magic tables in SQL Server refer to two special virtual tables inserted and deleted that are used in triggers. Inserted contains copies of the affected rows during INSERT and UPDATE operations, and deleted contains copies of the affected rows during DELETE and UPDATE operations.
Q26) What is SQL Injection?
Answer: SQL Injection is a technique where malicious SQL statements are inserted into an entry field for execution. This can allow attackers to gain unauthorized access to a database or manipulate its contents.
Q27) How can you prevent SQL Injection?
Answer: To prevent SQL Injection, use parameterized queries or prepared statements with bound parameters. These methods separate SQL code from user input, preventing the interpreter from confusing them.
Q28) What is a filtered index?
Answer: A filtered index is an index with a filter condition that allows it to include only a subset of rows in a table. It improves query performance and reduces index maintenance costs by excluding rows that are not needed by queries.
Q29) Clustered and Non-Clustered index. Which is used when?
Answer: Clustered index: Physically orders the data rows in the table based on the indexed column(s). Typically used on columns that are frequently searched for ranges of data. Non-Clustered index: Creates a separate structure (like a binary tree) for the indexed columns that points back to the original table rows. Useful for columns frequently used in queries for lookups but not for sorting the physical order of the table.
Q30) What is the virtual keyword?
Answer: In C#, the virtual keyword is used to modify a method, property, indexer, or event declaration and allow for it to be overridden in derived classes.
Q31) Have you worked on collections? What are the different collections available in C#?
Answer: C# provides several built-in collection types such as List, Dictionary, HashSet, Queue, Stack, etc., each optimized for different kinds of operations.
Q32) What is the difference between hash table and dictionary?
Answer: Both HashTable and Dictionary are key-value pair collections, but Dictionary is strongly typed and offers better performance than HashTable, which is weakly typed and considered obsolete in C#.
Q33) Which collection will give better performance - hash table or dictionary?
Answer: Dictionary generally provides better performance because it is strongly typed and more efficient due to its hash-based implementation compared to HashTable.
Q34) Can you explain where you have used collection objects in your project?
Describe where you have used collection objects (like lists, dictionaries) in your projects, emphasizing their role in managing and manipulating data efficiently.
Q35) What are the different components available in ADO.NET?
ADO.NET includes components such as Connection, Command, DataReader, DataAdapter, and DataSet, which facilitate data access and manipulation in .NET applications.
Q36) What is a dataset?
A DataSet is an in-memory cache of data retrieved from a data source, typically a database. It can hold multiple tables with relationships, constraints, and changes tracked in memory.
Q37) Can you talk about execute scalar and execute non-query commands?
ExecuteScalar is used to retrieve a single value (like a count or aggregate result) from a database, while ExecuteNonQuery is used for executing commands that do not return any data, such as INSERT, UPDATE, DELETE queries.
Q38) Have you used encryption? What is that?
Encryption is the process of transforming data into a secure form that can only be read or processed by those with the proper decryption key or algorithm.
Q39) What is the ideal timeout for a connection string?
The ideal timeout for a connection string depends on the specific application's requirements and network conditions. A typical value ranges from 15 to 30 seconds but can be adjusted based on the complexity of queries and the reliability of the network.