entity-framework – 未找到可执行文件匹配命令“dotnet-ef”

我正在做一个项目示例使用ASP.Net核心RC2与Microsoft.EntityFramework.Core和sqlite。

我遵循这个教程：
https://damienbod.com/2015/08/30/asp-net-5-with-sqlite-and-entity-framework-7/

但是，当我运行这个命令：

dotnet ef migrations add FirstMigration

我得到这个错误：

No executable found matching command "dotnet-ef"

这里是我的project.json配置：

{
  "dependencies": {
    "Microsoft.NETCore.App": {
      "version": "1.0.0-rc2-3002702","type": "platform"
    },"Microsoft.AspNetCore.Mvc": "1.0.0-rc2-final","Microsoft.AspNetCore.Server.IISIntegration": "1.0.0-rc2-final","Microsoft.AspNetCore.Server.Kestrel": "1.0.0-rc2-final","Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0-rc2-final","Microsoft.Extensions.Configuration.FileExtensions": "1.0.0-rc2-final","Microsoft.Extensions.Configuration.Json": "1.0.0-rc2-final","Microsoft.Extensions.Logging": "1.0.0-rc2-final","Microsoft.Extensions.Logging.Console": "1.0.0-rc2-final","Microsoft.Extensions.Logging.Debug": "1.0.0-rc2-final","Microsoft.EntityFrameworkCore": "1.0.0-rc2-final","Microsoft.EntityFrameworkCore.sqlite": "1.0.0-rc2-final"
  },"tools": {
    "Microsoft.AspNetCore.Server.IISIntegration.Tools": {
      "version": "1.0.0-preview1-final","imports": "portable-net45+win8+dnxcore50"
    }
  },"frameworks": {
    "netcoreapp1.0": {
      "imports": [
        "dotnet5.6","dnxcore50","portable-net45+win8"
      ]
    }
  },"buildoptions": {
    "emitEntryPoint": true,"preserveCompilationContext": true
  },"runtimeOptions": {
    "gcServer": true
  },"publishOptions": {
    "include": [
      "wwwroot","Views","appsetTings.json","web.config"
    ]
  },"scripts": {
    "postpublish": [ "dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%" ]
  }
}

"Microsoft.EntityFrameworkCore.Tools": {
  "version": "1.0.0-preview1-final","imports": [
    "portable-net45+win8+dnxcore50","portable-net45+win8"
  ]
}