Azure DevOps Self-hosted Agent: NETSDK1045: The current .NET SDK does not support targeting .NET 8.0

Recently I have faced this issue in one of our Self-hosted agents in Azure DevOps when a pipeline is trying to build a .NET 8.0 application.

C:\vsts-agent\_work\_tool\dotnet\sdk\5.0.405\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.TargetFrameworkInference.targets(141,5): 
 
error NETSDK1045: The current .NET SDK does not support targeting .NET 8.0.  
Either target .NET 5.0 or lower, or use a version of the .NET SDK that supports .NET 8.0. 
[C:\vsts-agent\_work\67\s\xxxxx.csproj]

The error was happening in a NuGetCommand@2 task while doing a restore. I replaced that with a DotNetCoreCLI@2. Then that step succeeded but eventually failed again in a VSBuild@1 task (that was using vsVersion: '17.0' which is the latest) for the same reason. 

This was strange because the pipeline was specifically requesting for .NET 8.0.

- task: UseDotNet@2
  displayName: Use .NET
  inputs:
    packageType: 'sdk'
    version: '8.0.x'

The pipeline had no reason to use .NET SDK 5.0.405 and had no idea where this specific version was coming from.

Then I started digging, and after scratching my head for a couple of hours, noticed the following in agent worker logs (usually inside C:\vsts-agent\_diag). To my surprise, the pipeline is getting executed with the following.

{
  ...
  "variables": {
    "DOTNET_MSBUILD_SDK_RESOLVER_SDKS_DIR": {
      "value": "C:\\vsts-agent\\_work\\_tool\\dotnet\\sdk\\5.0.405\\Sdks"
    },
    "DOTNET_MSBUILD_SDK_RESOLVER_SDKS_VER": {
      "value": "5.0.405"
    },
    ...
  }
  ...
}

DOTNET_MSBUILD_SDK_RESOLVER_* are .NET environment variables that are used to force the resolved SDK tasks and targets to come from a given base directory and report a given version to MSBuild.

• DOTNET_MSBUILD_SDK_RESOLVER_SDKS_DIR: Overrides the .NET SDK directory.
• DOTNET_MSBUILD_SDK_RESOLVER_SDKS_VER: Overrides the .NET SDK version.
• DOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR: Overrides the dotnet.exe directory path.

And that kind of answered where  .NET SDK 5.0.405 was coming from, but the question remains why. Submitted an Issue #19520: Self hosted agent uses incorrect DOTNET_MSBUILD_SDK_RESOLVER_SDKS_*.

To get past the issue, I had to override these variables. To test the concept, I have overridden these variables by passing .NET 8.0 counterpart values to the pipeline execution.

Passing variables to the pipeline execution

and that finally worked. But we can't be manually overriding these for each run, so I have overridden them in YAML as follows.

variables:
- name: DOTNET_MSBUILD_SDK_RESOLVER_SDKS_DIR
  value: 'C:\vsts-agent\_work\_tool\dotnet\sdk\8.0.101\Sdks'
- name: DOTNET_MSBUILD_SDK_RESOLVER_SDKS_VER
  value: '8.0.101'

...

Now the pipeline builds and publishes .NET 8 apps successfully, but I still have no idea why the older SDK was being forced.

Hopefully, we will find it here soon:

   #19520: Self-hosted agent uses incorrect DOTNET_MSBUILD_SDK_RESOLVER_SDKS_*

Hope this helps.

Happy Coding.

Regards,

Jaliya