The current .NET SDK does not support targeting .NET Core 2.1.3 - sdk

Question

I want to make sure that my application is built against .NET Core 2.1.3, so I installed version 2.1.401 of the SDK and set the TargetFrameworkVersion of the project to 2.1.3.
This gives me the following error message (emphasis mine):
C:\Program Files\dotnet\sdk\2.1.401\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.TargetFrameworkInference.targets(137,5): error NETSDK1045: The current .NET SDK does not support targeting .NET Core 2.1.3. Either target .NET Core 2.1 or lower, or use a version of the .NET SDK that supports .NET Core 2.1.3.
So the interesting thing is that the build seems to use the freshly installed SDK (2.1.401) - which is supposed to support .NET Core 2.1.3 - but it is still complaining that .NET Core 2.1.3 is not supported. This doesn't make sense to me...
What could be wrong here?

Answer 1

(For my answer I will assume that you're building a framework-dependent application and not a self-contained application.)
You cannot set 2.1.3 directly as the <TargetFramework> in the .csproj because it's just the patch version that's different.
Only the following entries are allowed: https://learn.microsoft.com/en-us/dotnet/standard/frameworks
So in your case the .csproj needs to have <TargetFramework>netcoreapp2.1</TargetFramework>.
But as Damir pointed out in the comment, you can force the version if you also add <RuntimeFrameworkVersion>2.1.3</RuntimeFrameworkVersion> to the <PropertyGroup>.
You can check the effect of this change if you open the "Manage NuGet Packages" dialog and look at the version of the metapackage Microsoft.NETCore.App that is implicitly being used.
Without the <RuntimeFrameworkVersion> it's 2.1.0, otherwise it should be 2.1.3.
But aside from that there are sometimes other factors as well that will implicitly determine the version that's being used.
For example, if you want to build a self-contained application you have to specify the <RuntimeIdentifier> which will also force the framework version to 2.1.3 because it will publish the highest patch runtime on your machine automatically.
That said, I wouldn't recommend to set any <RuntimeFrameworkVersion> manually for the most part.
Starting with .NET Core 2.1 all framework-dependent applications (that are built using .NET Core 2.0 or later) will automatically roll forward to the latest minor version that is installed if the original version of the runtime isn't present on the system.
So if you only have .NET Core 2.1.3 installed on the target system, your framework-dependent .NET Core 2.1.0 application will automatically use that runtime and framework.
You can read a bit more about the .NET Core version selection mechanism here.

Answer 2

I had the same issue and and was at the time using visual studio 2017 and had latest .net sdk installed(which at time of the post 2.2.401). Installing sdk 2.2.107 and adding it to the global.json file (I have it my project root) solved
the problem for me.
{
"sdk": {
"version": "2.2.107"
}
}
Also see this related post on the visual studio developer community forum.