Asp.net mvc 添加初始迁移实体框架7

当我尝试创建初始迁移时，出现了一个错误

我添加了命令和依赖项

  "dependencies": {

    "jQuery": "2.1.4",
    "Microsoft.AspNet.IISPlatformHandler": "1.0.0-rc1-final",
    "Microsoft.AspNet.Mvc": "6.0.0-rc1-final",
    "Microsoft.AspNet.Mvc.TagHelpers": "6.0.0-rc1-final",
    "Microsoft.AspNet.StaticFiles": "1.0.0-rc1-final",
    "EntityFramework.Core": "7.0.0-rc1-final",
    "EntityFramework.MicrosoftSqlServer": "7.0.0-rc1-final",
    "EntityFramework.Commands": "7.0.0-rc1-final",
    "Microsoft.AspNet.Hosting": "1.0.0-rc1-final",
    "Microsoft.AspNet.Server.Kestrel": "1.0.0-rc1-final"
  },

  "commands": {
    "web": "Microsoft.AspNet.Server.Kestrel",
    "ef": "EntityFramework.Commands"
  },

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知道为什么吗？

我可以用这个命令行解决这个问题

dnvm use 1.0.0-rc1-update1
dnx ef migrations add Initial