Script.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

using Microsoft.CodeAnalysis.CSharp.Scripting;
using Microsoft.CodeAnalysis.Scripting;

namespace EvalUITest
{
    class Script
    {
        ScriptState state;

        public static async Task<Script> Create(IEnumerable<Assembly> references, IEnumerable<string> usings)
        {
            var options = ScriptOptions.Default.WithReferences(references).WithImports(usings);
            var state = await CSharpScript.RunAsync("", options);
            return new Script() { state = state };
        }

        public async Task<object> ExecuteNext(string code)
        {
            state = await state.ContinueWithAsync(code);
            return state.ReturnValue;
        }
    }
}