Target frameworks

https://docs.microsoft.com/en-us/dotnet/standard/frameworks

When you target a framework in an app or library, you're specifying the set of APIs that you'd like to make available to the app or library. You specify the target framework in your project file using Target Framework Monikers (TFMs).

An app or library can target a version of .NET Standard. .NET Standard versions represent standardized sets of APIs across all .NET implementations. For example, a library can target .NET Standard 1.6 and gain access to APIs that function across .NET Core and .NET Framework using the same codebase.

An app or library can also target a specific .NET implementation to gain access to implementation-specific APIs. For example, an app that targets Xamarin.iOS (for example, Xamarin.iOS10) gets access to Xamarin-provided iOS API wrappers for iOS 10, or an app that targets the Universal Windows Platform (UWP, uap10.0) has access to APIs that compile for devices that run Windows 10.

For some target frameworks (for example, the .NET Framework), the APIs are defined by the assemblies that the framework installs on a system and may include application framework APIs (for example, ASP.NET).

For package-based target frameworks (for example, .NET Standard and .NET Core), the APIs are defined by the packages included in the app or library. A metapackage is a NuGet package that has no content of its own but is a list of dependencies (other packages). A NuGet package-based target framework implicitly specifies a metapackage that references all the packages that together make up the framework.

Latest target framework versions

The following table defines the most common target frameworks, how they're referenced, and which version of the .NET Standard they implement. These target framework versions are the latest stable versions. Pre-release versions aren't shown. A Target Framework Moniker (TFM) is a standardized token format for specifying the target framework of a .NET app or library.

Target Framework	Latest  Stable Version	Target Framework Moniker (TFM)	Implemented  .NET Standard Version
.NET Standard	2.0	netstandard2.0	N/A
.NET Core Application	2.0	netcoreapp2.0	2.0
.NET Framework	4.7.2	net472	2.0

Supported target framework versions

A target framework is typically referenced by a TFM. The following table shows the target frameworks supported by the .NET Core SDK and the NuGet client. Equivalents are shown within brackets. For example, win81 is an equivalent TFM to netcore451.

Target Framework	TFM
.NET Standard	netstandard1.0 netstandard1.1 netstandard1.2 netstandard1.3 netstandard1.4 netstandard1.5 netstandard1.6 netstandard2.0
.NET Core	netcoreapp1.0 netcoreapp1.1 netcoreapp2.0 netcoreapp2.1
.NET Framework	net11 net20 net35 net40 net403 net45 net451 net452 net46 net461 net462 net47 net471 net472
Windows Store	netcore [netcore45] netcore45 [win] [win8] netcore451 [win81]
.NET Micro Framework	netmf
Silverlight	sl4 sl5
Windows Phone	wp [wp7] wp7 wp75 wp8 wp81 wpa81
Universal Windows Platform	uap [uap10.0] uap10.0 [win10] [netcore50]

How to specify target frameworks

Target frameworks are specified in your project file. When a single target framework is specified, use the TargetFramework element. The following console app project file demonstrates how to target .NET Core 2.0:

XMLCopy

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.0</TargetFramework>
  </PropertyGroup>

</Project>

When you specify multiple target frameworks, you may conditionally reference assemblies for each target framework. In your code, you can conditionally compile against those assemblies by using preprocessor symbols with if-then-else logic.

The following library project file targets APIs of .NET Standard (netstandard1.4) and APIs of the .NET Framework (net40 and net45). Use the plural TargetFrameworks element with multiple target frameworks. Note how the Condition attributes include implementation-specific packages when the library is compiled for the two .NET Framework TFMs:

XMLCopy

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFrameworks>netstandard1.4;net40;net45</TargetFrameworks>
  </PropertyGroup>

  <!-- Conditionally obtain references for the .NET Framework 4.0 target -->
  <ItemGroup Condition=" '$(TargetFramework)' == 'net40' ">
    <Reference Include="System.Net" />
  </ItemGroup>

  <!-- Conditionally obtain references for the .NET Framework 4.5 target -->
  <ItemGroup Condition=" '$(TargetFramework)' == 'net45' ">
    <Reference Include="System.Net.Http" />
    <Reference Include="System.Threading.Tasks" />
  </ItemGroup>

</Project>

Within your library or app, you write conditional code to compile for each target framework:

C#Copy

public class MyClass
{
    static void Main()
    {
#if NET40
        Console.WriteLine("Target framework: .NET Framework 4.0");
#elif NET45  
        Console.WriteLine("Target framework: .NET Framework 4.5");
#else
        Console.WriteLine("Target framework: .NET Standard 1.4");
#endif
    }
}

The build system is aware of preprocessor symbols representing the target frameworks shown in the Supported target framework versions table. When using a symbol that represents a .NET Standard or .NET Core TFM, replace the dot with an underscore and change lowercase letters to uppercase (for example, the symbol for netstandard1.4 is NETSTANDARD1_4).

The complete list of preprocessor symbols for .NET Core target frameworks is:

Target Frameworks	Symbols
.NET Framework	NET20, NET35, NET40, NET45, NET451, NET452, NET46, NET461, NET462, NET47, NET471, NET472
.NET Standard	NETSTANDARD1_0, NETSTANDARD1_1, NETSTANDARD1_2, NETSTANDARD1_3, NETSTANDARD1_4, NETSTANDARD1_5, NETSTANDARD1_6, NETSTANDARD2_0
.NET Core	NETCOREAPP1_0, NETCOREAPP1_1, NETCOREAPP2_0, NETCOREAPP2_1

Deprecated target frameworks

The following target frameworks are deprecated. Packages targeting these target frameworks should migrate to the indicated replacements.

Deprecated TFM	Replacement
aspnet50 aspnetcore50 dnxcore50 dnx dnx45 dnx451 dnx452	netcoreapp
dotnet dotnet50 dotnet51 dotnet52 dotnet53 dotnet54 dotnet55 dotnet56	netstandard
netcore50	uap10.0
win	netcore45
win8	netcore45
win81	netcore451
win10	uap10.0
winrt	netcore45

See also

Packages, Metapackages and Frameworks
Developing Libraries with Cross Platform Tools
.NET Standard
.NET Core Versioning
dotnet/standard GitHub repository
NuGet Tools GitHub Repository
Framework Profiles in .NET