What is the difference between .NET Framework, .NET Core, and .NET 5+?

This tutorial explains the key differences between .NET Framework, .NET Core, and .NET 5+ (now just called .NET). Understanding these differences is crucial for choosing the right platform for your C# development needs.

Historical Context: The .NET Framework

.NET Framework (released in the early 2000s) was the original .NET implementation by Microsoft. It was designed primarily for Windows and provided a comprehensive framework for building Windows desktop applications, web applications (using ASP.NET), and services. Key characteristics include:

• Windows-centric: Designed to run primarily on Windows operating systems.
• Full Framework: Included a vast library of functionalities.
• CLR (Common Language Runtime): Managed execution environment for .NET code.
• Tightly coupled with Windows: Relied heavily on Windows-specific features.

The Rise of .NET Core: Cross-Platform Development

.NET Core was introduced as a cross-platform, open-source, and modular implementation of .NET. It was designed to address the limitations of .NET Framework and enable .NET development on macOS and Linux. Key characteristics include:

• Cross-Platform: Runs on Windows, macOS, and Linux.
• Open-Source: Developed under an open-source license (MIT license).
• Modular: You only include the components you need in your application, reducing its footprint.
• ASP.NET Core: A redesigned version of ASP.NET optimized for performance and cross-platform compatibility.
• CLR and CoreCLR: .NET Core used CoreCLR, a smaller and more modular runtime.

.NET 5+ (and beyond): Unification and the Future of .NET

.NET 5 (released in November 2020) marked a significant step towards unifying .NET Framework and .NET Core. It combined the best features of both platforms and set the stage for a single, unified .NET platform. Microsoft removed the 'Core' moniker and now it is simply called .NET.

• Unified Platform: A single base class library (BCL) and runtime for all .NET workloads.
• Cross-Platform: Continues to support Windows, macOS, and Linux.
• Improved Performance: Significant performance improvements compared to both .NET Framework and .NET Core.
• Modern Features: Includes support for the latest C# features and .NET APIs.
• Ongoing Development: Microsoft releases a new major version of .NET every November (e.g., .NET 6, .NET 7, .NET 8). Long Term Support (LTS) releases are released every two years.

Key Differences Summarized

Here's a table summarizing the key differences:

When to Use Which?

• .NET Framework: Use if you have existing, well-established Windows desktop applications (WPF or Windows Forms) that rely heavily on Windows-specific APIs and don't need to run on other platforms. Consider migrating to .NET if possible.
• .NET: Use for all new development. It's the future of .NET and provides the best performance, features, and cross-platform support.

Real-Life Use Case: Modern Web API

This example demonstrates a simple ASP.NET Core (now .NET) Web API controller. It illustrates the modern approach to web development using .NET, which is cross-platform and highly performant. This type of application would not be easily built on the .NET Framework without significant porting effort.

using Microsoft.AspNetCore.Mvc;

namespace MyWebApp.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class WeatherForecastController : ControllerBase
    {
        private static readonly string[] Summaries = new[]
        {
            "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
        };

        private readonly ILogger<WeatherForecastController> _logger;

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

        [HttpGet(Name = "GetWeatherForecast")]
        public IEnumerable<WeatherForecast> Get()
        {
            return Enumerable.Range(1, 5).Select(index => new WeatherForecast
            {
                Date = DateTime.Now.AddDays(index),
                TemperatureC = Random.Shared.Next(-20, 55),
                Summary = Summaries[Random.Shared.Next(Summaries.Length)]
            })
            .ToArray();
        }
    }
}

Best Practices

• Stay Updated: Keep your .NET SDK and runtime updated to the latest versions to benefit from performance improvements, security patches, and new features.
• Use NuGet: Leverage NuGet packages to manage dependencies and reuse existing libraries.
• Target Specific Frameworks: When creating libraries, target specific .NET versions to ensure compatibility. Consider targeting multiple versions if possible.
• Use the .NET CLI: The .NET CLI is a powerful tool for creating, building, and publishing .NET applications. Learn how to use it effectively.

Interview Tip

Be prepared to discuss the advantages of .NET (5+) over .NET Framework, particularly regarding cross-platform compatibility, performance, and open-source nature. Understand the concept of .NET Standard and its role in code sharing between different .NET implementations. Also mention the benefits of using .NET for microservices architectures because of its smaller memory footprint and faster startup times.

Memory Footprint

.NET Core and subsequent versions generally have a smaller memory footprint compared to .NET Framework. This is because they are more modular and allow you to include only the necessary components for your application. This is especially important for cloud deployments and microservices where resource efficiency is critical.