Dotnet build doesn't work with newcsproj and PackageReference

Question

Reproduce steps:

1. Open Visual Studio 2017, create new class library project, .NET 4.6.1 .
2. Add reference to Newtonsoft.Json with Nuget Package Manager.
3. Build project successfully with VS2017 .
4. Open command line and run dotnet build from project directory.

It gives the following error:

error CS0246: The type or namespace name 'Newtonsoft' could not be found (are you missing a using directive or an assembly reference?)

dotnet version:

Any ideas how to get rid of this error?

Edit: Before running dotnet restore:

After running dotnet restore

Edit with files: ClassLibrary1.csproj

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
  <PropertyGroup>
    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
    <ProjectGuid>{42A41D81-0A26-4D79-935E-6002BFAD37EB}</ProjectGuid>
    <OutputType>Library</OutputType>
    <AppDesignerFolder>Properties</AppDesignerFolder>
    <RootNamespace>ClassLibrary1</RootNamespace>
    <AssemblyName>ClassLibrary1</AssemblyName>
    <TargetFrameworkVersion>v4.6.1</TargetFrameworkVersion>
    <FileAlignment>512</FileAlignment>
  </PropertyGroup>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
    <DebugSymbols>true</DebugSymbols>
    <DebugType>full</DebugType>
    <Optimize>false</Optimize>
    <OutputPath>bin\Debug\</OutputPath>
    <DefineConstants>DEBUG;TRACE</DefineConstants>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
  </PropertyGroup>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
    <DebugType>pdbonly</DebugType>
    <Optimize>true</Optimize>
    <OutputPath>bin\Release\</OutputPath>
    <DefineConstants>TRACE</DefineConstants>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
  </PropertyGroup>
  <ItemGroup>
    <Reference Include="System" />
    <Reference Include="System.Core" />
    <Reference Include="System.Xml.Linq" />
    <Reference Include="System.Data.DataSetExtensions" />
    <Reference Include="Microsoft.CSharp" />
    <Reference Include="System.Data" />
    <Reference Include="System.Net.Http" />
    <Reference Include="System.Xml" />
  </ItemGroup>
  <ItemGroup>
    <Compile Include="Class1.cs" />
    <Compile Include="Properties\AssemblyInfo.cs" />
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="Newtonsoft.Json">
      <Version>9.0.1</Version>
    </PackageReference>
  </ItemGroup>
  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
</Project>

Class1.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace ClassLibrary1
{
    public class Class1
    {

        [JsonProperty]
        public string asd { get; set; }
    }
}

Answer 1

You're using the "old style" msbuild project, which won't work with the dotnet CLI.

Replace your whole project file with:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net461</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Newtonsoft.Json" Version="10.0.3" />
  </ItemGroup>

</Project>

Now it will be compatible with the dotnet CLI, and all should be well.

Answer 2

To reference a library on the command line you need to use the /r: compiler option. For example run csc /r:Path_to_your_DLL /t:Path_to_your_.cs_files

According to this microsoft doc , Visual studio seems to do the work of including all the libraries automatically when you use nuget inside visual studio, but since you are trying to build using command line, you have to manually reference all the libraries yourself.