10 .NET Architecture Interview Questions and Answers

.NET Architecture is a robust and versatile framework developed by Microsoft, designed to support the development and execution of applications across various platforms. It provides a comprehensive environment for building, deploying, and running applications, ranging from web and mobile to desktop and cloud-based solutions. With its extensive library and support for multiple programming languages, .NET Architecture is a critical skill for developers aiming to create scalable and high-performance applications.

This article offers a curated selection of interview questions focused on .NET Architecture. By working through these questions and their detailed answers, you will gain a deeper understanding of key concepts and best practices, enhancing your ability to articulate your knowledge and demonstrate your expertise in interviews.

.NET Architecture Interview Questions and Answers

1. Explain the role of the Common Language Runtime (CLR) in .NET architecture.

The Common Language Runtime (CLR) is the execution engine for .NET applications, providing services like memory management, security, exception handling, interoperability, Just-In-Time (JIT) compilation, and type safety. These features streamline development and enhance application performance.

2. Describe how the Global Assembly Cache (GAC) works and its purpose.

The Global Assembly Cache (GAC) is a repository for .NET assemblies shared by multiple applications on a machine. It resolves “DLL Hell” by ensuring the correct version of an assembly is loaded, using strong naming to prevent conflicts.

3. What are the key differences between .NET Core and .NET Framework?

.NET Core and .NET Framework are both Microsoft platforms with distinct characteristics. .NET Core is cross-platform, offering better performance and scalability, and supports flexible deployment options. It is more suitable for microservices and containerized applications. In contrast, .NET Framework is Windows-only and installed as a system-wide component. While both share many APIs, .NET Core has a smaller footprint and is supported by modern development tools like Visual Studio Code.

4. Explain the concept of middleware in ASP.NET Core.

Middleware in ASP.NET Core is a component in the application pipeline that handles requests and responses. It can perform actions before and after passing requests to the next component, useful for tasks like authentication, logging, and error handling.

Example:

public class RequestLoggingMiddleware
{
    private readonly RequestDelegate _next;

    public RequestLoggingMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        Console.WriteLine($"Request: {context.Request.Method} {context.Request.Path}");
        await _next(context);
        Console.WriteLine($"Response: {context.Response.StatusCode}");
    }
}

// In Startup.cs
public void Configure(IApplicationBuilder app)
{
    app.UseMiddleware<RequestLoggingMiddleware>();
    app.UseRouting();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}

5. Describe the microservices architecture and how you would implement it using .NET.

Microservices architecture in .NET can be implemented using ASP.NET Core for building services, Docker for containerization, and Kubernetes for orchestration. Service discovery tools like Consul, API Gateways like Ocelot, and event buses like RabbitMQ facilitate communication and management. Monitoring and logging tools like Prometheus and ELK Stack help maintain service health.

Example of a simple microservice using ASP.NET Core:

using Microsoft.AspNetCore.Mvc;

namespace ProductService.Controllers
{
    [ApiController]
    [Route("api/[controller]")]
    public class ProductsController : ControllerBase
    {
        [HttpGet]
        public IActionResult GetProducts()
        {
            var products = new List<string> { "Product1", "Product2", "Product3" };
            return Ok(products);
        }
    }
}

6. How would you implement logging in a .NET Core application?

In .NET Core, logging is built into the framework, supporting various providers like Console and Debug. Configure logging services in the Startup class and use dependency injection to inject the ILogger interface into classes.

Example:

using Microsoft.Extensions.Logging;

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddLogging(config =>
        {
            config.AddConsole();
            config.AddDebug();
        });
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILogger<Startup> logger)
    {
        logger.LogInformation("Application is starting up.");
    }
}

public class MyService
{
    private readonly ILogger<MyService> _logger;

    public MyService(ILogger<MyService> logger)
    {
        _logger = logger;
    }

    public void DoWork()
    {
        _logger.LogInformation("Doing work in MyService.");
    }
}

7. Describe how you would use gRPC in a .NET application.

gRPC is a high-performance framework for remote procedure calls, using HTTP/2 and Protocol Buffers. To use gRPC in .NET, define the service contract in a .proto file, generate server and client code, implement the service, and create a client to call it.

Example:

1. Define the service contract in a .proto file:

syntax = "proto3";

option csharp_namespace = "GrpcExample";

service Greeter {
  rpc SayHello (HelloRequest) returns (HelloReply);
}

message HelloRequest {
  string name = 1;
}

message HelloReply {
  string message = 1;
}

2. Generate the server and client code using the Protocol Buffers compiler (protoc).

3. Implement the gRPC service on the server:

public class GreeterService : Greeter.GreeterBase
{
    public override Task<HelloReply> SayHello(HelloRequest request, ServerCallContext context)
    {
        return Task.FromResult(new HelloReply
        {
            Message = "Hello " + request.Name
        });
    }
}

4. Create a gRPC client to call the service:

var channel = GrpcChannel.ForAddress("https://localhost:5001");
var client = new Greeter.GreeterClient(channel);
var reply = await client.SayHelloAsync(new HelloRequest { Name = "World" });
Console.WriteLine("Greeting: " + reply.Message);

8. How would you design a scalable .NET application to handle millions of requests per second?

Designing a scalable .NET application involves using microservices architecture, load balancing, caching, asynchronous processing, and database optimization. Implement message queuing and auto-scaling, and ensure comprehensive monitoring and logging.

9. Discuss how you would integrate a .NET application with cloud services like Azure.

Integrating a .NET application with Azure involves deploying to Azure App Services, using Azure SQL Database for data storage, and Azure Storage for unstructured data. Azure Functions can be used for serverless computing, enhancing functionality and scalability.

10. How would you design a robust API using .NET technologies?

Designing a robust API with .NET involves using a layered architecture, ASP.NET Core, and attribute-based routing. Ensure security with OAuth2 and JWT, validate data, handle errors globally, and integrate logging and monitoring. Use Swagger for documentation, implement API versioning, and write tests to ensure functionality.