- check Bin pour
System.Data.SqlClient.dll
- right-click solution > restore nuget packages
- check Bin pour
System.Data.SqlClient.dll
- Si l'erreur persist, manage nuget packages > uninstall/reinstall
System.Data.SqlClient
<compilation debug="true" targetFramework="4.6.1">
<assemblies>
<add assembly="netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51"/>
</assemblies>
</compilation>