Installing NuGet packages in Unity 2021

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NuGet is indispensable for working in .NET. Unfortunately, it takes a bit of work to get it working with Unity.

Unity only recognizes DLLs placed under the Assets folder, so we need a way to get the DLLs into the Assets folder. We cannot add the Nuget packages to the project files as we would for other .NET projects because Unity generates the sln and project files. This means that any NuGet packages that we have installed using the IDE will get wiped out by Unity.

There is an older guide that I found, which helped me figure out how to add NuGet packages into Unity. But, it had many steps that were irrelevant to Unity 2021.

As an example, we will look at installing Installing Microsoft.Extensions.DependencyInjection into an assembly definition.

Step 1: Install Nuget Package

Select the Manage NuGet Packages for Solution in your IDE.

Search and install the Microsoft.Extensions.DependencyInjection package

Installing Nuget Package Window

This will do a few things.

  1. Create an app.config file. This file can be deleted.
  2. Create a packages.config file. This file can be committed
  3. Download the Nuget package and its dependencies to the $(Solutiondir)/packages folder. This folder should be added to .gitignore

Packages Folder

Step 2: Make the DLL available to Unity

In the packages\Microsoft.Extensions.DependencyInjection.6.0.0/lib folder, you might see folders for different targets.

Target Frameworks

Copy the DLL from the netstandard2.1 folder into the Assets/Plugin/DI folder. Remember how Unity needs DLLs to be inside the Assets folder. I prefer to put the DLL into nested folders under Assets, so it's easier to manage multiple DLLs.

Step 3: Turn off Auto reference

By default, all predefined assemblies and assembly definitions can automatically reference the DLL. In most cases, we want a DLL to be exposed only to specific assembly definitions.

Turn off Auto reference in the import settings for the DLL and click Apply.

Turn Off Auto Reference

Step 4: Add the DLL as a reference to the assembly definition

Select override references in the assemblies that need this package and add the DLLs to the assembly references.

Add Reference To DLL


Error: Unloading broken assembly Assets/Plugins/DI/Microsoft.Extensions.DependencyInjection.dll, this assembly can cause crashes in the runtime

Copy the DLL from packages\Microsoft.Extensions.DependencyInjection.Abstractions.6.0.0\lib\netstandard2.1 to the Assets/Plugin/DI folder. It is because Unity needs the Microsoft.Extensions.DependencyInjection.Abstractions.dll.

Bonus: Installing Moq into an assembly definition for Tests

Repeat the steps for Moq and make the appropriate changes

After Unity recompiling, you will see an error in the unity console.

Mog Error

To fix this, copy the Castle.Core.dll from the packages folder and put it in the same folder as Moq.dll.


NuGet allows us to install useful DLLs. I have shown how you can install NuGet packages into Unity 2021.