DotNetCoreProjectMigrator.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Xml;
using System.Xml.Linq;
using System.Xml.XPath;
using System.Linq;
using System.Text;

namespace CsProjectMigrator
{
    public class Migrator
    {
        public void Migrate(string csProjectFilePath)
        {
            string projectDirectory = Path.GetDirectoryName(csProjectFilePath);

            if (string.IsNullOrWhiteSpace(projectDirectory))
                throw new InvalidOperationException();

            

            //Get the project references
            var project = new CsProject(csProjectFilePath);

            string packagesConfigPath = Path.Combine(projectDirectory, "packages.config");

            PackagesConfig packagesConfig = null;

            if (File.Exists(packagesConfigPath))
            {
                packagesConfig = new PackagesConfig(packagesConfigPath);
            }

            StringBuilder text = new StringBuilder();

            text.AppendLine("<Project Sdk=\"Microsoft.NET.Sdk\">");

            text.AppendLine("  <PropertyGroup>");
            text.AppendLine("    <TargetFrameworks>netstandard2.0;net46</TargetFrameworks>");
            text.AppendLine("  </PropertyGroup>");

            text.AppendLine();

            if (project.ProjectReferences.Any())
            {
                text.AppendLine("  <ItemGroup>");

                foreach (var projectReference in project.ProjectReferences)
                {
                    text.AppendLine($"    <ProjectReference Include=\"{projectReference}\" />");
                }

                text.AppendLine("  </ItemGroup>");

                text.AppendLine();
            }

            if (packagesConfig != null && packagesConfig.Packages.Any())
            {

                text.AppendLine("  <ItemGroup>");

                foreach (var package in packagesConfig.Packages)
                {
                    text.AppendLine($"    <PackageReference Include=\"{package.Id}\" Version=\"{package.Version}\" />");
                }
                
                text.AppendLine("  </ItemGroup>");
            }

            text.AppendLine("</Project>");

            //Back up the project file
            File.Move(csProjectFilePath, csProjectFilePath + ".bak");

            //Write out the new one
            File.WriteAllText(csProjectFilePath, text.ToString());

            //Console.WriteLine(text.ToString());
        }

        public class CsProject
        {
            public List<string> ProjectReferences { get; } = new List<string>();

            public CsProject(string path)
            {
                //Load up the project
                XDocument projectDocument = XDocument.Load(path);

                XmlNamespaceManager xnm = new XmlNamespaceManager(new NameTable());
                xnm.AddNamespace("x", "http://schemas.microsoft.com/developer/msbuild/2003");
                
                const string query = "/x:Project/x:ItemGroup/x:ProjectReference";

                var projectReferenceElements = projectDocument.XPathSelectElements(query, xnm);

                foreach (var reference in projectReferenceElements)
                {
                    ProjectReferences.Add(reference.Attribute("Include")?.Value);
                }
            }
        }

        public class Package
        {
            public string Id { get; set; }

            public string Version { get; set; }
        }

        public class PackagesConfig
        {
            public List<Package> Packages { get; } = new List<Package>();

            public PackagesConfig(string path)
            {
                //Load up the project
                XDocument configDocument = XDocument.Load(path);

                var packages = configDocument.XPathSelectElements("/packages/package");

                foreach (var package in packages)
                {
                    string id = package.Attribute("id").Value;
                    string version = package.Attribute("version").Value;

                    Packages.Add(new Package()
                    {
                        Id = id,
                        Version = version
                    });
                }
            }

        }

        
    }
}