Could not get the reflection type for DbContext

I had this issue too, when I was using the new C#7 feature (expression bodied members and Throw expressions) but by replacing my code with it's equivalent in C#6 it didn't give me that error anymore. Try to test your project without any C#7 new feature and probably it should works fine. I'm not sure what is the reason but I think The Roslyn packages that scaffolding depends on does not support C#7 new features yet.

As a workaround to let scaffolding works with C#7 I think you can by doing the following:

1. Install (or update) NuGet package Microsoft.CodeAnalysis.CSharp.Workspaces version 2.0.0 or higher
2. And then retry to scaffolding again

I'm using visual studio 2019 and .Net Core 3.1

I just realized that somewhere in my code I had used unsafe { } block. I commented unsafe code for temporary and I can scaffold again.