DevOps: SQL Server - NETFramework v4.5 not found

Case
I have a DevOps pipeline to build and deploy my Azure SQL Server Database, but it is giving an .NET Framework error stating that it can't find the framework version. It did work before, how can I solve it?

error MSB3644: The reference assemblies for
 .NETFramework,Version=v4.5 were not found.

The entire error message in Azure DevOps:

##[section]Starting: 1. Creating Artifact
==============================================================================
Task         : MSBuild
Description  : Build with MSBuild
Version      : 1.199.0
Author       : Microsoft Corporation
Help         : https://docs.microsoft.com/azure/devops/pipelines/tasks/build/msbuild
==============================================================================
##[command]"D:\a\_tasks\MSBuild_c6c4c611-aa2e-4a33-b606-5eaba2196824\1.199.0\ps_modules\MSBuildHelpers\vswhere.exe" -version [17.0,18.0) -latest -format json
##[command]"C:\Program Files\Microsoft Visual Studio\2022\Enterprise\MSBuild\Current\Bin\msbuild.exe" "D:\a\1\s\SQL\myDWH\myDWH.sqlproj" /nologo /nr:false /dl:CentralLogger,"D:\a\_tasks\MSBuild_c6c4c611-aa2e-4a33-b606-5eaba2196824\1.199.0\ps_modules\MSBuildHelpers\Microsoft.TeamFoundation.DistributedTask.MSBuild.Logger.dll";"RootDetailId=|SolutionDir=D:\a\1\s\SQL\myDWH|enableOrphanedProjectsLogs=true"*ForwardingLogger,"D:\a\_tasks\MSBuild_c6c4c611-aa2e-4a33-b606-5eaba2196824\1.199.0\ps_modules\MSBuildHelpers\Microsoft.TeamFoundation.DistributedTask.MSBuild.Logger.dll"  /p:_MSDeployUserAgent="VSTS_3aa34741-51f2-4a22-9768-a5deca3bfa4e_build_17_0"
Build started 5/13/2022 2:36:44 PM.
##[error]C:\Program Files\Microsoft Visual Studio\2022\Enterprise\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(1221,5): Error MSB3644: The reference assemblies for .NETFramework,Version=v4.5 were not found. To resolve this, install the Developer Pack (SDK/Targeting Pack) for this framework version or retarget your application. You can download .NET Framework Developer Packs at https://aka.ms/msbuild/developerpacks
Project "D:\a\1\s\SQL\myDWH\myDWH.sqlproj" on node 1 (default targets).
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(1221,5): error MSB3644: The reference assemblies for .NETFramework,Version=v4.5 were not found. To resolve this, install the Developer Pack (SDK/Targeting Pack) for this framework version or retarget your application. You can download .NET Framework Developer Packs at https://aka.ms/msbuild/developerpacks [D:\a\1\s\SQL\myDWH\myDWH.sqlproj]
_CleanRecordFileWrites:
  Creating directory "obj\Debug\".
Done Building Project "D:\a\1\s\SQL\myDWH\myDWH.sqlproj" (default targets) -- FAILED.

Build FAILED.

"D:\a\1\s\SQL\myDWH\myDWH.sqlproj" (default target) (1) ->
(GetReferenceAssemblyPaths target) -> 
  C:\Program Files\Microsoft Visual Studio\2022\Enterprise\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(1221,5): error MSB3644: The reference assemblies for .NETFramework,Version=v4.5 were not found. To resolve this, install the Developer Pack (SDK/Targeting Pack) for this framework version or retarget your application. You can download .NET Framework Developer Packs at https://aka.ms/msbuild/developerpacks [D:\a\1\s\SQL\myDWH\myDWH.sqlproj]

    0 Warning(s)
    1 Error(s)

Time Elapsed 00:00:01.97
##[error]Process 'msbuild.exe' exited with code '1'.
##[section]Finishing: 1. Creating Artifact

Solution
This error is probably because you have a DevOps agent of the type windows-latest and that recently changed to the newer Windows-2022 and .Net Framework version 4.5 is out of support since April 26, 2022.

The solution is simple:

• Go to Visual Studio and open your database project
• Find your project in the Solution Explorer pane
• Right click your project and go to the properties
• Go to the tab SQLCLR and find Target framework
• Change the .NET Framework to a higher version (4.7.2 or 4.8)
• Now save your project and make sure the change goes to your repository so that your build pipeline can do its work correctly

Change .NET Framework version in SQLCLR pane

Another option is to downgrade your DevOps Agent from 'windows-latest' to 'windows-2019'. An even simpler change, but probably only a temporary change to postpone the real change.

Conclusion

In this post you learned how to solve the .NET framework not found error in two ways. A temporary quick-win by changing the agent type and a little more 'permanent' change in the Visual Studio project (until that versio also goes out of support).