A full-featured calculator using built-in methods

Calc.cs

using Microsoft.CSharp;
using System;
using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Calc
{
    public partial class Form1 : Form //5
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            CSharpCodeProvider provider = new CSharpCodeProvider();
            CompilerParameters parameters = new CompilerParameters();
            // True - memory generation, false - external file generation
            parameters.GenerateInMemory = true;
            // True - exe file generation, false - dll file generation
            parameters.GenerateExecutable = false;

            parameters.ReferencedAssemblies.Add("Calc.exe");

            string input = inputTextBox.Text;
            string pattern = "(\\d+)";
            string replacement = "Convert.ToDouble(${1})";
            Regex rgx = new Regex(pattern);
            input = rgx.Replace(input, replacement);

            string code = @"using System;
                            public class Program : Calc.IOperation
                            {
                                public double Do()
                                {
                                    return " + input + @";
                                }
                            }";

            CompilerResults results = provider.CompileAssemblyFromSource(parameters, code);

            if (results.Errors.HasErrors)
            {
                StringBuilder sb = new StringBuilder();

                foreach (CompilerError error in results.Errors)
                {
                    sb.AppendLine(String.Format("Error ({0}): {1}", error.ErrorNumber, error.ErrorText));
                }

                label1.Text = sb.ToString();
                return;
            }

            Type type = results.CompiledAssembly.GetTypes().First(t => typeof(IOperation).IsAssignableFrom(t));
            IOperation op = (IOperation)Activator.CreateInstance(type, false);
            label1.Text = op.Do().ToString();
        }
    }
}