This is a ASP.NET controller that can execute C# code that is POSTed to it.

InteractiveController.cs

// Created by Sam Wronski
// Find more of my work at: worldofzero.com and youtube.com/WorldOfZeroDevelopment
//
// WARNING: This controller exposes the .NET runtime as a web endpoint.
// This could allow third parties to run arbitrary code on your system
// which would be very harmful to your computer and could compromise
// your personal devices and information.
// If you choose to run this inside of a cloud runtime this would also
// make it possible in some cases for people with access to this endpoint
// to exfiltrate details about the current environment (like Secrets!)

using System.Text;
using Microsoft.AspNetCore.Mvc;
using Microsoft.CodeAnalysis.CSharp.Scripting;
using Microsoft.CodeAnalysis.Scripting;

namespace WorldOfZero.DotNetEvaluator.Controllers;

[ApiController]
[Route("evaluator/csharp")]
public class EvaluatorController : ControllerBase
{
    private readonly ILogger<EvaluatorController> _logger;

    public EvaluatorController(ILogger<EvaluatorController> logger)
    {
        _logger = logger;
    }

    [HttpPost(Name = "EvaluateCsharp")]
    public async Task<object> Post([FromBody]string[] code)
    {
        var resultsSet = new List<dynamic>();
        
        var builder = new StringBuilder();
        ScriptState state = null;

        Script script = null;
        
        // Execute line by line and save the results after each line to assist with debugging later
        foreach (var line in code)
        {
            if (script == null || state == null)
            {
                script = CSharpScript.Create(line);
                state = await script.RunAsync();
            }
            else
            {
                state = await state.ContinueWithAsync(line);
            }
            
            Console.WriteLine(line);
            builder.AppendLine(line);

            var scriptCode = builder.ToString();
            var variables = state.Variables.Select(v => new { name = v.Name, value = v.Value }).ToArray();
            resultsSet.Add(new
            {
                Script = scriptCode,
                Result = state.ReturnValue,
                Variables = variables,
                Exception = state.Exception
            });
        }

        var hash = Convert.ToString(script.GetHashCode(), 16) + Convert.ToString(DateTime.Now.GetHashCode(), 16);
        
        return new
        {
            Logs = $"https://localhost:7272/logs/{hash}", // todo runewake2: this doesn't go anywhere yet and is just a placeholder - fix that.
            Trace = resultsSet,
            Result = state?.ReturnValue
        };
    }
}