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Understanding the .NET Standard Library

By David Li on 2023-05-12T13:35:03.000Z

Understanding the .NET Standard Library

The .NET Standard Library is a foundational element of the .NET ecosystem. In this article, we’ll explore the purpose and benefits of the .NET Standard Library, its versioning strategy, and how it enables seamless interoperability between different .NET implementations.

What is the .NET Standard Library?

The .NET Standard Library is a specification of APIs (Application Programming Interfaces) that define a consistent set of base class libraries (BCL) across various .NET implementations. It is not an implementation itself but acts as a contract that different .NET platforms, such as .NET Core, .NET Framework, and Xamarin, must adhere to.

The primary goal of the .NET Standard Library is to promote code sharing and reusability across different .NET platforms. It achieves this by providing a common set of APIs that developers can rely on when building .NET applications, regardless of the target platform.

Why do we need the .NET Standard Library?

Before the introduction of the .NET Standard Library, developers faced challenges when trying to share code across different .NET platforms. Each platform had its own BCL, which led to inconsistencies and incompatibilities between APIs.

These discrepancies made it difficult to create portable class libraries (PCLs), which aimed at providing a common set of APIs for multiple platforms. PCLs were often limited in functionality, and targeting multiple platforms resulted in complex project configurations and versioning nightmares.

The .NET Standard Library solves these issues by providing a single, well-defined set of APIs that all .NET implementations must support. This promotes code sharing and compatibility across platforms, making it easier for developers to create applications that target multiple .NET platforms.

Versioning and Compatibility

The .NET Standard Library follows a versioning strategy that defines a growing set of APIs with each new version. Each version of the .NET Standard Library is backward compatible, meaning that a higher version includes all APIs from previous versions.

For example, if you have a library that targets .NET Standard 1.4, it will be compatible with all .NET implementations that support .NET Standard 1.4 or higher.

The versioning strategy also allows for easier platform support. If a platform supports a specific version of the .NET Standard Library, it is guaranteed to support all lower versions as well.

How does the .NET Standard Library work?

When you create a .NET project targeting a specific version of the .NET Standard Library, you are essentially committing to use only the APIs defined by that version. This ensures that your code will be compatible with any .NET platform that supports your targeted .NET Standard Library version.

To consume a .NET Standard Library, the target platform must provide an implementation for the APIs defined by the library’s version. This implementation is often referred to as a “platform extension,” and it ensures that the platform adheres to the .NET Standard Library contract.

Benefits of the .NET Standard Library

The .NET Standard Library offers several advantages for developers:

  1. Code Sharing: Libraries targeting the .NET Standard Library can be used across all .NET platforms, reducing code duplication and promoting reusability.

  2. Consistent APIs: The .NET Standard Library provides a stable and well-defined set of APIs, helping developers avoid platform-specific differences and incompatibilities.

  3. Simplified Versioning: The backward-compatible versioning strategy of the .NET Standard Library streamlines targeting multiple platforms, making it easier to manage dependencies and project configurations.

  4. Future-Proofing: As the .NET ecosystem evolves and introduces new platforms, the .NET Standard Library ensures that your code remains compatible and easy to maintain.


The .NET Standard Library is a crucial element of the .NET ecosystem, acting as a bridge between different .NET implementations. It promotes code sharing, reusability, and compatibility across platforms, allowing developers to create more robust and maintainable applications. By understanding and leveraging the .NET Standard Library, developers can harness these benefits and build high-quality, cross-platform applications with ease.

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