Updating your NuGet references

Sometimes you get an annoying error after updating your .NET Framework or some of the packages or libraries in your project: "Some NuGet packages were installed using a target framework different from the current target framework and may need to be reinstalled. Visit http://docs.nuget.org/docs/workflows/reinstalling-packages for more information. Packages affected: <name-of-nuget-package>".

The problem stems from the fact that NuGet packages have variants for different .NET flavors and in your project they are "hinted" at by the <HintPath> child element in the <Reference> elements in your .csproj file. Somehow, the hint still points to a different variant than the one you need and that's why you get this error. The explanation in length can be found in this great post: Why, when and how to reinstall NuGet packages after upgrading a project, but just in case his blog disappears (as so many great ones did in the past), here is the gist of the solution:

In Visual Studio go to Tools → NuGet Package Manager → Package Manager Console and type:

Update-Package <name-of-nuget-package> -Reinstall -ProjectName <name-of-project>

To add some value to Derriey's post, you can solve all the similar issues in your solution by copying the entire list of errors from all projects by going to the Output pane, selecting them all and right clicking Copy, then run search and replace in your favorite editor with this regular expression:

^.*?Visit http://docs.nuget.org/docs/workflows/reinstalling-packages for more information.  Packages affected: ((?:[^,\s]+(?:, )?)+)\t([^\t]+)\t\t\d+\t\t$

and replacement pattern

Update-Package $1 -Reinstall -ProjectName $2

Then make sure there is only one project on each line, copy paste the result into the Package Manager Console window and the entire solution will get fixed.

Example: Error Some NuGet packages were installed using a target framework different from the current target framework and may need to be reinstalled. Visit http://docs.nuget.org/docs/workflows/reinstalling-packages for more information. Packages affected: Microsoft.Extensions.Configuration, Serilog MyProject.Common 0

Turns into: Update-Package Microsoft.Extensions.Configuration, Serilog -Reinstall -ProjectName MyProject.Common Since Update-Package only supports one package and regex replace doesn't have a syntax for multiple captures in the same group, you will have to manually turn this into:

Update-Package Microsoft.Extensions.Configuration -Reinstall -ProjectName MyProject.Common
Update-Package Serilog -Reinstall -ProjectName MyProject.Common

Copy paste the result and the two projects will be reinstalled on the affected projects in your solution.