Below are best-practice answers to the common interview questions I listed earlier. These answers are designed to be concise, clear, and demonstrate your expertise.
.NET Questions
1. What is the difference between IEnumerable and IQueryable?
IEnumerable:Works with in-memory collections (e.g., List, Array).
Executes queries on the client side (LINQ-to-Objects).
Suitable for small datasets.
IQueryable:Works with remote data sources (e.g., databases).
Executes queries on the server side (LINQ-to-Entities).
Suitable for large datasets and optimized for performance.
Example:
IEnumerable<Customer> customers = db.Customers.Where(c => c.Age > 30).ToList(); // Executes in memory IQueryable<Customer> customers = db.Customers.Where(c => c.Age > 30); // Executes on the database server
2. How does dependency injection work in ASP.NET Core?
Dependency Injection (DI) is a design pattern used to achieve Inversion of Control (IoC) between classes and their dependencies.
How it works:
Services are registered in the
Startup.csorProgram.csfile usingservices.AddSingleton,services.AddScoped, orservices.AddTransient.The framework injects these services into controllers, views, or other services via constructor injection.
Example:
public void ConfigureServices(IServiceCollection services) { services.AddScoped<IMyService, MyService>(); // Register service } public class MyController : Controller { private readonly IMyService _myService; public MyController(IMyService myService) // Inject service { _myService = myService; } }
3. Explain the lifecycle of a .NET application.
Compilation:
Source code is compiled into Intermediate Language (IL) by the C# compiler.
Execution:
The Common Language Runtime (CLR) loads the IL code and compiles it into machine code using Just-In-Time (JIT) compilation.
Memory Management:
The Garbage Collector (GC) automatically manages memory allocation and deallocation.
Application Domains:
.NET applications run in isolated environments called application domains.
4. What is the difference between Task and Thread in C#?
Thread:Represents an actual OS-level thread.
Resource-intensive and harder to manage.
Task:Represents an asynchronous operation.
Uses the ThreadPool for efficient resource management.
Supports
async/awaitfor easier asynchronous programming.
Example:
// Thread Thread thread = new Thread(() => DoWork()); thread.Start(); // Task Task.Run(() => DoWork());
5. How do you handle exceptions globally in ASP.NET Core?
Use middleware to handle exceptions globally.
Example:
public void Configure(IApplicationBuilder app, IHostingEnvironment env) { if (env.IsDevelopment()) { app.UseDeveloperExceptionPage(); } else { app.UseExceptionHandler("/Home/Error"); // Global exception handler } }
Azure Questions
1. What is the difference between Azure App Service and Azure Functions?
Azure App Service:
Used for hosting web applications, APIs, and mobile backends.
Supports multiple languages and frameworks.
Ideal for long-running applications.
Azure Functions:
Serverless compute service for event-driven tasks.
Executes code in response to triggers (e.g., HTTP, timers, queues).
Ideal for short-lived, stateless functions.
2. How do you secure an Azure SQL Database?
Authentication:
Use Azure Active Directory (AAD) or SQL authentication.
Authorization:
Implement Role-Based Access Control (RBAC).
Encryption:
Enable Transparent Data Encryption (TDE) for data at rest.
Use SSL/TLS for data in transit.
Firewall Rules:
Restrict access to specific IP addresses or virtual networks.
3. Explain the difference between Azure Blob Storage and Azure Table Storage.
Azure Blob Storage:
Used for storing unstructured data like images, videos, and documents.
Supports tiered storage (Hot, Cool, Archive).
Azure Table Storage:
NoSQL key-value store for structured data.
Ideal for storing metadata or semi-structured data.
4. How do you implement CI/CD using Azure DevOps?
Steps:
Create a repository in Azure DevOps.
Define a build pipeline (e.g., using YAML) to compile and test the code.
Define a release pipeline to deploy the application to Azure.
Use triggers to automate the process (e.g., on code push).
Example:
trigger: branches: include: - main pool: vmImage: 'windows-latest' steps: - task: UseDotNet@2 inputs: packageType: 'sdk' version: '6.x' - script: dotnet build --configuration Release - script: dotnet test
5. What is the purpose of Azure Active Directory (AAD)?
AAD is a cloud-based identity and access management service.
Key Features:
Single Sign-On (SSO) for applications.
Multi-Factor Authentication (MFA) for enhanced security.
Integration with on-premises Active Directory.
Full Stack Questions
1. How do you optimize the performance of a web application?
Frontend:
Minify and bundle CSS/JS files.
Use lazy loading for images and components.
Backend:
Optimize database queries and use caching (e.g., Redis).
Use asynchronous programming to avoid blocking threads.
Infrastructure:
Scale horizontally using load balancers.
Use Content Delivery Networks (CDNs) for static assets.
2. What are the differences between REST and GraphQL?
REST:
Uses fixed endpoints for resources.
Over-fetching or under-fetching of data can occur.
GraphQL:
Uses a single endpoint for all queries.
Clients can request only the data they need.
3. How do you handle state management in a frontend application?
Local State:
Use component state (e.g., React
useState).
Global State:
Use state management libraries like Redux or Context API.
Server State:
Use libraries like React Query or SWR for caching and synchronization.
4. Explain the concept of microservices and when to use them.
Microservices:
Architectural style where applications are built as a collection of small, independent services.
When to Use:
For large, complex applications requiring scalability and flexibility.
When different teams work on different parts of the application.
5. How do you ensure security in a full stack application?
Authentication:
Use OAuth, JWT, or AAD for secure authentication.
Authorization:
Implement role-based access control (RBAC).
Data Protection:
Encrypt sensitive data at rest and in transit.
Input Validation:
Sanitize user inputs to prevent SQL injection and XSS attacks.