Get the download count for all versions of a package

ConsoleApp17.csproj

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

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp3.1</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="NuGet.Protocol" Version="5.5.0-preview.1.6319" />
  </ItemGroup>

</Project>

Program.cs

using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using NuGet.Common;
using NuGet.Configuration;
using NuGet.Protocol.Core.Types;

namespace ConsoleApp17
{
    public class Program
    {
        public static async Task Main(string[] args)
        {
            var source = new PackageSource("https://api.nuget.org/v3/index.json");
            var providers = Repository.Provider.GetCoreV3();
            var repository = new SourceRepository(source, providers);

            var searchResource = await repository.GetResourceAsync<PackageSearchResource>();
            var searchFilter = new SearchFilter(includePrerelease: true);

            var results = await searchResource.SearchAsync("packageId:Newtonsoft.Json", searchFilter, skip: 0, take: 1, NullLogger.Instance, CancellationToken.None);
            if (results.Count() != 1)
            {
                throw new InvalidOperationException($"Expected 1 result, found {results.Count()}");
            }

            var package = results.First();

            Console.WriteLine($"Package {package.Identity.Id} has {package.DownloadCount} total downloads across all versions");

            foreach (var version in await package.GetVersionsAsync())
            {
                Console.WriteLine($"Found version {version.Version.ToNormalizedString()} with {version.DownloadCount} downloads");
            }
        }
    }
}

zOutput

Package Newtonsoft.Json has 363187770 total downloads across all versions
Found version 3.5.8 with 360077109 downloads
Found version 4.0.1 with 360077109 downloads
Found version 4.0.2 with 360077109 downloads
Found version 4.0.3 with 360077109 downloads
Found version 4.0.4 with 360077109 downloads
Found version 4.0.5 with 360077109 downloads
Found version 4.0.6 with 360077109 downloads
Found version 4.0.7 with 360077109 downloads
Found version 4.0.8 with 360077109 downloads
Found version 4.5.1 with 360077109 downloads
Found version 4.5.2 with 360077109 downloads
Found version 4.5.3 with 360077109 downloads
Found version 4.5.4 with 360077109 downloads
Found version 4.5.5 with 360077109 downloads
Found version 4.5.6 with 360077109 downloads
Found version 4.5.7 with 360077109 downloads
Found version 4.5.8 with 360077109 downloads
Found version 4.5.9 with 360077109 downloads
Found version 4.5.10 with 360077109 downloads
Found version 4.5.11 with 360077109 downloads
Found version 5.0.1 with 360077109 downloads
Found version 5.0.2 with 360077109 downloads
Found version 5.0.3 with 360077109 downloads
Found version 5.0.4 with 360077109 downloads
Found version 5.0.5 with 360077109 downloads
Found version 5.0.6 with 360077109 downloads
Found version 5.0.7 with 360077109 downloads
Found version 5.0.8 with 360077109 downloads
Found version 6.0.1 with 360077109 downloads
Found version 6.0.2 with 360077109 downloads
Found version 6.0.3 with 360077109 downloads
Found version 6.0.4 with 360077109 downloads
Found version 6.0.5 with 360077109 downloads
Found version 6.0.6 with 360077109 downloads
Found version 6.0.7 with 360077109 downloads
Found version 6.0.8 with 360077109 downloads
Found version 7.0.1 with 360077109 downloads
Found version 8.0.1 with 360077109 downloads
Found version 8.0.2 with 360077109 downloads
Found version 8.0.3 with 360077109 downloads
Found version 9.0.1 with 360077109 downloads
Found version 10.0.1 with 360077109 downloads
Found version 10.0.2 with 360077109 downloads
Found version 10.0.3 with 360077109 downloads
Found version 11.0.1 with 360077109 downloads
Found version 11.0.2 with 360077109 downloads
Found version 12.0.1 with 360077109 downloads
Found version 12.0.2 with 360077109 downloads
Found version 12.0.3 with 360077109 downloads