Build Failed Error While migration of the dotnet core entity framework

To remove this error check your code manually if every thing in the code you write is okay…

if your code is okay check the .csproj file…
write the following code if not present..
<ItemGroup>    <Folder Include=”wwwroot\”/>  </ItemGroup>

after again write migration command:
go to (project manager console) PM> dotnet ef migrations add YourMigrationName

If still not solved look at:https://stackoverflow.com/questions/44785540/ef-core-add-migration-build-failed/47775946