When developing with the .NET ecosystem, understanding the difference between .NET Core and .NET Standard Class Library project types is crucial for ensuring compatibility and maximum efficiency of your applications. Both are a part of Microsoft’s .NET implementation but serve different purposes for developers.

.NET Core

.NET Core is an open-source, general-purpose development platform maintained by Microsoft and the .NET community on GitHub. It is cross-platform, supporting Windows, macOS, and Linux, and can be used to build device, cloud, and IoT applications.

.NET Core was created to build modern, cloud-based, internet-connected applications, such as web apps, IoT apps, and mobile backends. It was designed to provide a modular platform that allows developers the flexibility to bring all the necessary dependencies for their app with them, rather than relying on an existing installation of .NET on the target environment. This "self-contained" deployment model can be very advantageous when multiple applications requiring different versions of .NET are deployed on the same server.

.NET Standard

.NET Standard isn’t a framework or runtime environment but rather a formal specification of .NET APIs that are intended to be available on all .NET implementations. The motive behind .NET Standard was to establish greater uniformity in the .NET ecosystem. .NET Standard is a contract; it’s a set of APIs that all .NET implementations must provide. This simplifies .NET development and enhances cross-platform compatibility between different .NET flavors.

The key motive for .NET Standard is code sharing. For instance, if you create a class library based on the .NET Standard, it can be used across different .NET implementations like .NET Core, .NET Framework, and Xamarin.

Differences Explained

When choosing between which type of class library to develop, consider whether you need cross-platform capabilities and what platforms you intend to support.

• Compatibility: .NET Core libraries are compatible with .NET Core apps or any platform supporting .NET Core. However, .NET Standard libraries are designed to be usable in applications that implement any version of the .NET Standard, across all .NET implementations, including .NET Core, .NET Framework, and Xamarin.
• APIs: .NET Core libraries can use any API that is a part of .NET Core, including those not in the .NET Standard. Conversely, .NET Standard libraries can only use APIs that are included in the .NET Standard.
• Versatility: .NET Standard provides greater flexibility if you expect your code to run across different .NET platforms. .NET Core is optimized for building highly scalable systems and has APIs that might not be available in .NET Standard.

Technical Examples

Consider a scenario where you're developing a library to perform cryptographic functions, something generally useful across different applications:

1public class EncryptionService
2{
3    public string Encrypt(string data)
4    {
5        // Example encryption method
6    }
7
8    public string Decrypt(string data)
9    {
10        // Example decryption method
11    }
12}

If this library is something you foresee being used in .NET Core apps as well as in Xamarin mobile apps, you should target .NET Standard. But if features specific to .NET Core are required for performance or additional capabilities, then a .NET Core-specific library would be the right choice.

Summary Table

To conclude, the choice between a .NET Core and a .NET Standard class library primarily hinges on your specific needs for compatibility and platform support. Understanding these differences is essential for making strategic decisions in your .NET development projects.