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Using Reflection.Emit to Precompile Expressions to MSIL

, 6 Jan 2009 CPOL
The classes in this project allow you to parse text expressions entered by a user and compile them to a .NET assembly. This assembly can be executed on the fly, or saved to a DLL.
MSILParserProject.zip
MSILParserProject
MSILParser
bin
Debug
MSILParser.vshost.exe
ClassDiagram1.cd
ildasm.exe
MSILParser.csproj.user
MSILParser_TemporaryKey.pfx
Properties
Settings.settings
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;
using System.Reflection;
using System.Reflection.Emit;
using System.Diagnostics.SymbolStore;




namespace MSILParser
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                lblResults.Text = "";
                int n = Convert.ToInt32(numericUpDown1.Value);
                
                // Parse the expression and build our dynamic method
                MsilParser em = new MsilParser();
                Type t = em.CompileMsil(textBox1.Text);
                
                // Get a typed delegate reference to our method. This is very 
                // important for quick efficient calls!
                MethodInfo m = t.GetMethod("RunExpression");
                Delegate d = Delegate.CreateDelegate(typeof(MsilParser.ExpressionInvoker<Object>), m);
                MsilParser.ExpressionInvoker<Object> method = (MsilParser.ExpressionInvoker<Object>)d;
 
                // Start the timer
                Object result = null;
                Stopwatch st = new Stopwatch();
                st.Start();

                // Make a call to the method N-times
                for (int i = 0; i < n; i++)
                {
                    result = method();
                }

                // Stop the timer and output results
                st.Stop();
                lblResults.Text = ("Expression Value: " + result.ToString() + "\n" +
                    "Evaluation Time: " + st.Elapsed.ToString() + "\n") +
                    "Number of Iterations: " + n;

                // Save the Assembly and generate the MSIL code with ILDASM.EXE
                string modName = "expression.dll";
                Process p = new Process();
                p.StartInfo.FileName = "ildasm.exe";
                p.StartInfo.Arguments = "/text /nobar \"" + modName;
                p.StartInfo.UseShellExecute = false;
                p.StartInfo.CreateNoWindow = true;
                p.StartInfo.RedirectStandardOutput = true;
                p.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
                p.Start();

                string s = p.StandardOutput.ReadToEnd();
                p.WaitForExit();
                p.Close();
                txtMsil.Text = s;

            }
            catch (Exception ex)
            {
                lblResults.Text = "Could not parse: \n"+ex.Message;
            }
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            if (textBox1.Text.Length == 0)
                btnParse.Enabled = false;
            else
                btnParse.Enabled = true;
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }



    
    
    
    
    
    }
}

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License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Steve Marsh
Software Developer (Senior)
United States United States
Stephen Marsh has over 10 years of experience developing enterprise applications built on the .Net framework. He specializes in building expert systems that serve the financial industry.

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