NuGet packages

Don't reinvent the wheel

The Base Class Library covers a lot, but not everything. Need to generate PDFs, talk to a specific database, or write tests with nicer assertions? Someone has probably already written and published a library for it — as a NuGet package.

• NuGet is .NET's package manager (like npm for JavaScript or pip for Python).
• nuget.org is the public gallery where packages are published.
• A package is a zip file (.nupkg) containing compiled assemblies plus metadata, including the packages it depends on.

Adding a package

dotnet add package Humanizer

This does two things: it downloads the package, and records it in your .csproj:

<ItemGroup>
  <PackageReference Include="Humanizer" Version="2.14.1" />
</ItemGroup>

Now you can use it:

using Humanizer;
 
Console.WriteLine(TimeSpan.FromMinutes(90).Humanize());   // "1 hour, 30 minutes"
Console.WriteLine("some_variable_name".Humanize());       // "Some variable name"

Managing packages

dotnet add package Humanizer --version 2.14.1   # a specific version
dotnet list package                             # what this project uses
dotnet list package --outdated                  # which ones have updates
dotnet remove package Humanizer                 # remove it

Restore and the package cache

Packages aren't stored in your project folder. They're downloaded once into a global cache (~/.nuget/packages) and shared by all your projects. Restore is the step that makes sure every PackageReference is in the cache — dotnet build, run and test do it automatically.

That's why you commit the .csproj but never the packages themselves: anyone who clones the repository gets identical packages on their first build.

Reading version numbers

NuGet uses semantic versioning: MAJOR.MINOR.PATCH.

A version with a suffix, like 9.0.0-preview.3, is a prerelease.

Choosing packages wisely

Every package you add is code you're trusting and maintaining. Before adding one, check on nuget.org:

• Downloads and maintenance — is it widely used and recently updated?
• License — MIT and Apache-2.0 are common and permissive.
• Do you need it? — if it saves you three lines, it's not worth a dependency.

Packages you'll meet in this course

Key takeaways

• NuGet is the .NET package manager; nuget.org is the public gallery.
• dotnet add package downloads a package and adds a PackageReference to the .csproj.
• Packages live in a shared cache and are restored automatically on build.
• Versions follow MAJOR.MINOR.PATCH — be careful with major upgrades.