#if NET40 // Work around a bug in .NET 4.0's ConcurrentDictionary UseLegacyFallback(); #else UseModernAPI(); #endif

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If you cannot run installers (e.g., on a restricted build server), you can copy reference assemblies from a development machine:

NuGet also uses multi-targeting concepts. A single NuGet package can contain multiple versions of a library, each in a folder named for the target framework (e.g., net40 , net45 , net48 ). When installing such a package into a project that targets .NET Framework 4.6, NuGet automatically selects the assembly from the net45 folder, because that is the highest available version that is still less than or equal to 4.6.

Support legacy Windows systems easily.

Metadata-only copies of the .NET libraries. They contain signatures but no executable code.

A larger bundle that includes both the targeting pack and the full runtime for that version.

As part of this effort, Microsoft released various updates, such as the . This pack added support for designing and developing applications for the Update 4.0.3 Beta of Microsoft .NET Framework 4 using Microsoft Visual Studio 2010 SP1 or later. It added new reference assemblies, IntelliSense files, and other supporting files.

Pre-install the .NET Framework 4.8 Developer Pack on your build image. For Docker, add a layer:

A is essentially a set of reference assemblies that correspond to a particular version of the .NET Framework platform. Unlike the actual runtime assemblies used to execute an application, reference assemblies contain metadata and API signatures but lack actual method bodies or internal logic. They serve as a blueprint that tells the compiler which APIs are available in a specific .NET Framework version.

While end-users only need the standard .NET runtime to execute applications, developers rely on multi-targeting packs to manage software deployment across multiple, shifting framework versions. This article explains exactly what the .NET Framework 4 Multi-Targeting Pack does, how it fits into the modern development ecosystem, and how to resolve common installation bugs. What is a Multi-Targeting Pack?

Providing a single installation command for full version development. Why Is It Still Relevant?

You are mixing a project that targets .NET 4.0 with a project or NuGet package that uses .NET 4.5+ APIs. The multi-targeting pack correctly flags this ambiguity.