gistfile1.txt

using System;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Text;
using System.Text.Json;
using Microsoft.AspNetCore.Mvc;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.Text;

namespace TestCompile.Controllers
{
    [Route("api")]
    [ApiController]
    public class CheckCodeController : Controller
    {
        [HttpPost]
        [Route("CheckCode")]
        public ActionResult<CheckCodeResponse> CheckCode([FromBody] CheckCodeRequest request)
        {
            //https://www.damirscorner.com/blog/posts/20190802-CompilingAndExecutingCodeInACsApp.html
            var syntaxTree = SyntaxFactory.ParseSyntaxTree(SourceText.From(request.CodeSample));

            var assemblyPath = Path.ChangeExtension(Path.GetTempFileName(), "exe");
            System.IO.File.WriteAllText(
                Path.ChangeExtension(assemblyPath, "runtimeconfig.json"),
                GenerateRuntimeConfig()
            );

            var dotNetCoreDir = Path.GetDirectoryName(typeof(object).GetTypeInfo().Assembly.Location);
            //https://laurentkempe.com/2019/02/18/dynamically-compile-and-run-code-using-dotNET-Core-3.0/
            var compilation = CSharpCompilation.Create(Path.GetFileName(assemblyPath))
                .WithOptions(new CSharpCompilationOptions(OutputKind.ConsoleApplication))
                .AddReferences(
                    MetadataReference.CreateFromFile(typeof(object).GetTypeInfo().Assembly.Location),
                    MetadataReference.CreateFromFile(typeof(Console).GetTypeInfo().Assembly.Location),
                    MetadataReference.CreateFromFile(Path.Combine(dotNetCoreDir, "System.Runtime.dll")),
                    MetadataReference.CreateFromFile(typeof(System.Runtime.AssemblyTargetedPatchBandAttribute).Assembly.Location),
                    MetadataReference.CreateFromFile(typeof(Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo).Assembly.Location)
                )
                .AddSyntaxTrees(syntaxTree);

            var result = compilation.Emit(assemblyPath);
            string outputData = "No Data";

            if (result.Success)
            {
                //https://stackoverflow.com/questions/4291912/process-start-how-to-get-the-output
                var startInfo = new ProcessStartInfo("dotnet", assemblyPath)
                {
                    RedirectStandardOutput = true,
                    RedirectStandardError = true,
                    UseShellExecute = false
                };
                var process = new Process() { StartInfo = startInfo };
                process.Start();
                StreamReader reader = process.StandardOutput;
                var errorOutput = process.StandardError.ReadToEnd();
                //https://github.com/dotnet/roslyn/issues/33090
                string output = reader.ReadToEnd();

                outputData = string.IsNullOrEmpty(errorOutput) ? output : errorOutput;
            }
            else
            {
                Debug.Write(string.Join(
                    Environment.NewLine,
                    result.Diagnostics.Select(diagnostic => diagnostic.ToString())
                ));
            }
        
            return new CheckCodeResponse()
            {
                Result = result.Success ? outputData : string.Join(
                    Environment.NewLine,
                    result.Diagnostics.Select(diagnostic => diagnostic.ToString())
                )};
        }
    
        private string GenerateRuntimeConfig()
        {
            using (var stream = new MemoryStream())
            {
                using (var writer = new Utf8JsonWriter(
                    stream,
                    new JsonWriterOptions() { Indented = true }
                ))
                {
                    writer.WriteStartObject();
                    writer.WriteStartObject("runtimeOptions");
                    writer.WriteStartObject("framework");
                    writer.WriteString("name", "Microsoft.NETCore.App");
                    writer.WriteString(
                        "version",
                        RuntimeInformation.FrameworkDescription.Replace(".NET ", "")
                    );
                    writer.WriteEndObject();
                    writer.WriteEndObject();
                    writer.WriteEndObject();
                }

                return Encoding.UTF8.GetString(stream.ToArray());
            }
        }
    }
}