Recently while upgrading a couple of projects to .NET Core 2.2, I came across this error.
This version of Microsoft.AspNetCore.App is only compatible with the netcoreapp2.1 target framework.
Please target netcoreapp2.1 or choose a version of Microsoft.AspNetCore.App compatible with netcoreapp2.2.
A quick google revealed that actually people had the same issue when their projects were going from 2.0 to 2.1 too. And all the fixes seemed kinda flaky and typically involved “Try this and pray” type steps.
To be honest, I know how to fix diagnose and fix the issue, but I don’t really know why that particular error message is the one that comes up.
First thing I noticed is that this error will only ever happen when you’ve tried opening a project in Visual Studio and tried to build. In some cases I’ve been able to build using the dotnet CLI, but not inside Visual Studio. If after building in Visual Studio, I then try and build from the dotnet CLI tool, I then start getting this error too. However if I delete the bin folder and rebuild from the CLI, we are all clear.
Next, in all cases the version of .NET Core I want to target is not available and not selected for my project inside VS. So if I right click my project and view properties, the Target Framework is blank :
This is because the version of Visual Studio that I’m using doesn’t actually support the version of .NET Core I am trying to run. It’s sort of this weird situation where even if you have the correct .NET Core SDK installed, that really only sets you up for using the dotnet CLI and writing code in something like VSCode.
All you need to do is update Visual Studio. Let me put that in big bold letters so people coming from Google can get their answer fast :
You Need To Update Visual Studio
Hopefully that’s clear enough!
Even once you update Visual Studio, you will likely need to delete the bin and obj folders of your project and then rebuild again from VS. Now there may be one very edge case that this doesn’t resolve your issues. And that’s if you are using the very latest preview builds for .NET Core SDK that Visual Studio either doesn’t support yet, or only supports in the Pre-Release version of VS. Rare, but it does happen.