How to use nuget library SimpleHelpers.FileEncoding on c# on VScode

dotnet add package SimpleHelpers.FileEncoding

SimpleHelpers.FileEncoding

dotnet run

it shows:

C:\Users\user\Downloads\c2\Program.cs(1,7): Error CS0246: The type or namespace name 'SimpleHelpers' could not be found (are you missing a using directive or an assembly reference?) [C:\Users\user\Downloads\c2\c2.csproj]

Program.cs:

using SimpleHelpers.FileEncoding;

namespace c2;
class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Hello, World!");
        var encoding = FileEncoding.DetectFileEncoding (@"D:\b\big5\LanTingJiXu_big5.txt");
    }
}

c2.csproj:

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

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="SimpleHelpers.FileEncoding" Version="1.4.0" />
  </ItemGroup>

</Project>

update the error message.

Solution

It looks like this package was authored to use the content folder with a .cs.pp file transform that were previously rendered and copied to the project folder for projects using packages.config to reference NuGet packages.

This is no longer supported for SDK-style projects which use PackageReference. The package author would need to switch to (or add) contentFiles to support PackageReference or create a pre-built binary (.dll file).