Build failed when trying to addmigration and update database

There all I am new to asp.net core. I have built a simple project on asp.net core 2.  

<ItemGroup>

    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.3" />

   <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="2.0.1" PrivateAssets="All" />

    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="2.0.1" PrivateAssets="All" />

  </ItemGroup>

I have all this references in my project. My code base does not have any error. My project compiles perfectly well. But I dont know why I can not add a migration or update my database.

I have the same problem when I create a new template on my Visual Studio 2017. Please what is the problem ?