The .NET framework includes a vast collection of reusable libraries and frameworks that allow developers to solve common problems and build applications more efficiently. With new .NET libraries and updates being released all the time, it can be difficult for developers to keep up with what libraries they should be using. While there are many great .NET libraries, some stand out as being particularly important and useful for most .NET developers to learn.
In this post, we will highlight 10 of the most popular, widely used, and modern .NET libraries that every developer working with .NET should familiarize themselves with. We'll briefly explore the key capabilities of each library and why they are useful additions to any .NET developer's toolkit. The libraries covered range from data access, web development, testing, serialization, mapping, and resilience.
Even if you don't end up using all these libraries directly, understanding what they do and the value they provide is useful context for any .NET developer. Our goal is that after reading this post, you will have a solid foundational knowledge of some of the most essential libraries to improve your .NET development skills and build more powerful applications faster. Whether you are new to .NET or an experienced developer looking to expand your knowledge, this overview of the top 10 libraries will have something valuable for you.
1. Entity Framework
The Entity Framework (EF) is Microsoft's primary data access technology for .NET applications. It provides an object-relational mapper (ORM) that enables .NET developers to work with databases using .NET objects. The biggest benefit of EF is that it abstracts away all the complexity of interacting with databases through things like SQL queries, allowing developers to work with collections of .NET objects simply. Some key capabilities of EF include:
Mapping .NET classes to database tables through configuration.
Automatically generating SQL for creating, querying, updating and deleting data.
Changing Tracking: EF keeps track of changes made to entity objects and persists those changes to the database.
Lazy Loading: related entities can be automatically loaded from the database when accessed.
Caching: query results are cached to optimize performance.
Migrations: allows creation and deployment of incremental database changes.
For any .NET application that needs to persist data in a relational database, Entity Framework is the go-to library for abstracting data access. It's been improved and optimized through several major releases, and most .NET developers will interact with EF at some point.
2. ASP.NET Core
ASP.NET Core is Microsoft's modern, cross-platform framework for building web applications. It provides a "batteries included" experience for quickly spinning up web APIs and sites. Some of the major capabilities it includes:
Model-View-Controller (MVC) framework for clean architecture.
Razor syntax for combining HTML markup with C# code.
Routing for mapping URLs to controllers/actions.
Dependency injection container.
Configuration framework.
Logging.
Data access - integrates with EF Core.
Authentication - supports OAuth, OpenID, and more.
Bundling and minimization.
Caching.
ASP.NET Core runs on Windows, Mac, or Linux and can be hosted standalone or in Docker containers. It's fast, extensible, and has a rich ecosystem of open-source libraries. Any .NET developer working on web apps should learn ASP.NET Core.
3. .NET Logging Frameworks
Logging is a crucial tool for outputting diagnostic information during an application's runtime. .NET has multiple logging frameworks that make adding logging straightforward. The two most popular options:
Serilog: A 3rd party framework that most in the .NET community prefer. Very flexible, creates structured log data, and integrates with many sinks (file, database, etc). Has a clean fluent API.
Microsoft.Extensions.Logging: Microsoft's built-in logging library included with ASP.NET Core. Integrates with many .NET classes through DI container. Supports logging scopes. More basic than Serilog but easier to use out of the box in ASP.NET Core apps.
Other popular logging libraries like NLog and log4net are also used extensively in .NET world. But Serilog and Microsoft.Extensions.Logging are good choices for most scenarios.
4. Newtonsoft Json.NET
JSON is the ubiquitous data interchange format used for web APIs and other integrations. For working with JSON in .NET code, Json.NET is the leading library. Key features:
Serialize/deserialize objects to/from JSON.
LINQ-style query API for parsing JSON.
Handle common JSON scenarios like missing data and caching.
Extensive configuration options for controlling serialization.
High performance.
Microsoft also provides System.Text.Json for JSON handling but many still prefer Json.NET for the time being due to its maturity and feature set. Json.NET is a must-have tool for any API development.
5. xUnit
xUnit is the most popular testing framework used by .NET developers. It provides a fluent API for creating unit tests targeting .NET code. Features include:
Attributes to decorate test methods (Fact, Theory, etc).
Assertions for validating logic.
Mocking frameworks like Moq integrate nicely.
Extensibility for custom assertions.
Runs tests in parallel for efficiency.
Other test frameworks like NUnit and MSTest are also used, but xUnit tends to be most preferred these days. Writing unit tests with xUnit is essential for any serious .NET project.
6. AutoMapper
When working with object-oriented code, a common need is translating between model types. For example, translating between domain model objects used in business logic and data transfer objects used in an API. AutoMapper does this easily:
Map between different object types through configuration.
Handle nested object translations.
Inject mapping logic into services/repositories.
Generate parsing code automatically.
It saves tons of time manually writing parsing code. AutoMapper is extremely useful in enterprise applications with layered architecture.
7. FluentValidation
Validating user input is crucial for any application. FluentValidation provides a clean way to declare validation logic for .NET classes using a fluent interface and lambda expressions. Such as:
public class PersonValidator : AbstractValidator<Person> {
public PersonValidator() {
RuleFor(x => x.Name).NotEmpty();
RuleFor(x => x.Age).InclusiveBetween(0, 120);
}
}
Other features include:
Custom validation methods.
Property & object level validation.
Support for async/IObservable.
Localization.
Extensible and pluggable.
FluentValidation abstracts away messier validation code into a clear format. Useful for validating commands, requests DTOs, business objects, etc.
8. Polly
Polly is a .NET resilience and transient fault-handling library that allows developers to express policies like Retry, Circuit Breaker, Timeout, etc. For example:
var policy = Policy.Handle<HttpResponseException>()
.Retry(3);
policy.Execute(() => CallHttpService());
Key features:
Fluent API for resilience policies.
Handles errors like network issues and timeouts.
Can wrap calls to unreliable services.
Great for implementing resilience patterns.
Pluggable and extensible architecture.
It is essential in distributed systems where services may fail randomly. Polly makes it easy to implement resilience best practices.
9. Automapper
Automapper is a library that makes it easy to map between different object types in .NET code. For example mapping between domain models and data transfer objects. Key features:
Define mappings between types through configuration.
Transform nested object graphs.
Handle different property names.
Inject mapping logic into services/repositories.
Generate mapping code automatically.
It eliminates tons of boilerplate code for translating between models/DTOs manually. AutoMapper is hugely useful for enterprise applications with layered architecture.
10. Swagger
When building web APIs, Swagger (OpenAPI) is essential for providing interactive documentation. It can generate a UI from API code, allowing users to browse endpoints, submit test requests, and get responses. Key features:
Generates OpenAPI spec from code comments.
Useful UI for testing API calls.
Integrates with MVC and WebAPI frameworks.
Validate payloads against schemas.
OpenAPI ecosystem supports code generation.
Swagger transforms bare APIs into rich, documented services for other teams to easily consume. It's a must-have for any public or large internal APIs.
Final Thoughts
The .NET ecosystem contains a vast collection of reusable libraries and frameworks that allow developers to solve common problems and build applications more efficiently. With new .NET libraries and updates being released all the time, it can be difficult for .NET developers to keep up with the most useful libraries to learn. While there are many great .NET libraries, some stand out as being particularly important for most .NET developers to master.
In this post, we will highlight 10 of the most essential, modern .NET libraries that any developer working with .NET should familiarize themselves with. We'll briefly explore the key capabilities of each library and why they are useful tools for any .NET developer's toolkit. The libraries covered range from data access, web development, testing, serialization, mapping, and resilience.
Even if you don't end up using all these libraries directly, understanding what they do and the value they provide is foundational knowledge for any .NET developer. Our goal is that after reading this post, you will have a solid grasp of some of the most widely used .NET libraries to improve your skills and build more powerful applications faster. Whether you are new to .NET or an experienced developer looking to expand your knowledge, this overview of the top 10 libraries will have something valuable for you.
For companies looking to hire .NET developers, these libraries represent essential skills and knowledge that competent .NET developers should possess. A developer well-versed in libraries like Entity Framework, ASP.NET Core, xUnit, and others demonstrates a strong understanding of modern .NET development best practices. When evaluating .NET candidates, look for hands-on experience with these top libraries.