如果涉及多个项目，注意保持DbContext所在项目和启动项目关于数据库的包引用版本一致
注意设置不同的DbContext迁移文件目录不同
1.Enable-migrations
EntityFrameworkCore\Enable-migrations –ContextTypeName:Namespace.TestDbContext1 –MigrationDirectory:MigrationDirectory1
EntityFrameworkCore\Enable-migrations –ContextTypeName:Namespace.TestDbContext2 –MigrationDirectory:MigrationDirectory2
2.Add-Migration
EntityFrameworkCore\Add-migration migration_name -Context TestDbContext1 -OutputDir MigrationDirectory1
必须指明-Context参数，参数为DbContext类名
3.update-database
EntityFrameworkCore\update-database -Context TestDbContext1
其他
存在多个DbContext的时候不指名Context的报错内容
More than one DbContext was found. Specify which one to use. Use the '-Context' parameter for PowerShell commands and the '--context' parameter for dotnet commands.
参考资料
Entity Framework Core tools reference - Package Manager Console in Visual Studio
Entity Framework - Multiple DbContext
Code First Migration in Multiple DbContext