خطا در نصب پکیج ها در پروژه

سلام استاد امیدوارم سالم وتندرست باشید من بعد از نصب هر پکیج با این خطا مواجه 

Severity Code Description Project File Line Suppression State

Error MSB3644 The reference assemblies for .NETFramework,Version=v5.0 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 LearnStore.Core C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets 1175