然后提示Startup project 'MRA.Model.csproj' targets framework '.NETStandard'. There is no runtime associated with this framework, and projects targeting it cannot be executed directly. To use the Entity Framework
Core .NET Command-line Tools with this project, add an executable project targeting .NET Core or .NET Framework that references this project, and set it as the startup project using --startup-project; or, update this project to cross-target .NET Core or .NET Framework. For more information on using the EF Core Tools with .NET Standard projects, see https://go.microsoft.com/fwlink/?linkid=2034781