Hi sorahuziu-8438,
First, I made a test in visual studio 2019 and target framework is .NET Core 3.1.
We can see from the picture below that we can't add System.Data.Entity.Design.dll in the project.
And I also create a same project in VS2019 and target framework is .NET Framework 4.8. It works fine.
Best Regards,
Daniel Zhang
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