What Broke in the Build
The .NET SDK selected for this build is older than the project’s target framework, so the SDK cannot build or restore it.
Fix the underlying build failure
Check SDK selection from the same shell or CI step with dotnet --info, install the required .NET SDK or update global.json, and re-run with dotnet build.
Prove the Build Path Is Clean
dotnet build succeeds without NETSDK1045, and dotnet --info shows the intended SDK version.
Validation
Re-run the failing command and confirm the original code/message is gone, and confirm expected artifacts or outputs exist (packages restored, build/publish succeeds).
Why the Build Fails
Usually this comes down to CI or the local machine has an older .NET SDK installed than the project requires, global.json pins an older SDK, or multiple SDK installs exist and PATH or resolver selection picks the wrong one.
Typical Output
error NETSDK1045: The current .NET SDK does not support targeting .NET 10.0. Either target .NET 9.0 or lower, or use a version of the .NET SDK that supports .NET 10.0.Mechanism
The SDK validates the project’s TargetFramework values early in MSBuild evaluation. If the TFM is newer than what the installed SDK supports, it stops with NETSDK1045.
Keep Build Prerequisites Consistent
To prevent this, pin SDK version with global.json and explicit CI installation, and add an early CI check that enforces a minimum dotnet --version.
Docs and source code
NETSDK1045 message template
User-facing message template. - GitHub
<data name="UnsupportedTargetFrameworkVersion" xml:space="preserve">
<value>NETSDK1045: The current .NET SDK does not support targeting {0} {1}. Either target {0} {2} or lower, or use a version of the .NET SDK that supports {0} {1}. Download the .NET SDK from https://aka.ms/dotnet/download</value>
<comment>{StrBegins="NETSDK1045: "}</comment>
</data>