Target nuget packege for multiple framework

When you’re building a .Net liibrary you have to take in care which framework the end user will use. In order to avoid user’s framework upgrade/downgrade we must target multiple frameworks in the nuget package.

Library project configuration

First, in your .csproj file, create separate build configurations. I created “Debug” | “Release” and “Debug45” | “Release45” for the target frameworks 4.6.1 and 4.5 respectively. I manually set the OutputPath and added theTargetFrameworkVersion element to each configuration:

<PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug45|AnyCPU'">
<PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Release45|AnyCPU'">

In this way you can build the library with different target framework.

Targeting Multiple Frameworks in NuGet

In the folder created for the nuget package divide the lib folder by adding for each targeted framework the relative folder where you will add the relative library .dll file.

The lib folder looks like this:

  • lib
    • net45
    • net461

Now you can run nuget.exe pack MyAssembly.nuspec

A new package is created.

When you refer this package through Nuget package manager from a VS solution, your reference automatically link the dll related to your project framework.


Nuget: How to reinstall and update packages

There are a number of situations when you need to reinstall and update nuget packages for a VS project.

One of this situations is when you wanna upgrade or downgrade the .NET Framework.

In this situation the most important Nuget functionality is Reinstalling packages with dependencies:

Update-Package –reinstall

reinstalls the same version of the original package, but installs the latest version of dependencies unless specific version constraints are provided. This allows you to update only the dependencies as required to fix an issue. However, if this rolls a dependency back to an earlier version, you can use

Update-Package <dependency_name>

to reinstall that one dependency without affecting the dependent package.

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