How do I list all installed NuGet packages?

In the NuGet Package Manager Console, enter the following command:

Get-Package

This will either print out a list of installed packages, or if none are present write the following line to the console:

PM> Get-PackageNo packages installed.

For more details, have a look at the NuGet PowerShell Reference.

If you just do

Get-Package

it will list the packages and where they are referenced. It will list the same packages over and over again if you have them referenced many times. If you want to get a clean list of all packages installed in the solution you can do

Get-Package | select -Unique Id, Versions

Get-Package -ProjectName "Your.Project.Name"

Will show the packages for the specified project.

See also: Package Manager Console PowerShell Reference

Note that each project will have a packages.config file which is used to track installed packages. If this is altered (specifically if you alter it backwards), the projects may not automatically download the correct package version. In that case, make a note of the packages required and do a uninstall-package, followed by a install-package for each.

Also, backups are your friend! ;)