Channels ▼
RSS

Generating Code at Run Time With Reflection.Emit


Generating Code at Run Time With Reflection.Emit

Listing 1: The HelloReflectionEmit class

using System;
using System.Reflection;
using System.Reflection.Emit;

class HelloReflectionEmit
{
    static void Main()
    {
        // Create a (weak) assembly name
        AssemblyName an = new AssemblyName();
        an.Name = "HelloReflectionEmit";

        // Define a new dynamic assembly (to be written to disk)
        AppDomain ad = AppDomain.CurrentDomain;
        AssemblyBuilder ab = 
            ad.DefineDynamicAssembly(an, 
            AssemblyBuilderAccess.Save);

        // Define a module for this assembly
        ModuleBuilder mb = ab.DefineDynamicModule(an.Name, 
            "Hello.exe");

        // namespace Foo { public class Bar { ... } }
        TypeBuilder tb = mb.DefineType("Foo.Bar", 
            TypeAttributes.Public|
            TypeAttributes.Class);

        // The leg bone's connected to the knee bone...
        MethodBuilder fb = tb.DefineMethod("Main", 
            MethodAttributes.Public|
            MethodAttributes.Static, 
            typeof(int), 
            new Type[] {typeof(string[])});

        // Write the ubiquitous "Hello, World!" method, in IL
        ILGenerator ilg = fb.GetILGenerator();

        ilg.Emit(OpCodes.Ldstr, "Hello, World!");
        ilg.Emit(OpCodes.Call, 
            typeof(Console).GetMethod("WriteLine", 
                new Type[] {typeof(string)} ));

        ilg.Emit(OpCodes.Ldc_I4_0);
        ilg.Emit(OpCodes.Ret);

        // Seal the lid on this type
        Type t = tb.CreateType();

        // Set the entrypoint (thereby declaring it an EXE)
        ab.SetEntryPoint(fb,PEFileKinds.ConsoleApplication);

        // Save it
        ab.Save("Hello.exe");

        // Done!
        Console.WriteLine("File saved: {0}", "Hello.exe");
    }
}


Related Reading


More Insights






Currently we allow the following HTML tags in comments:

Single tags

These tags can be used alone and don't need an ending tag.

<br> Defines a single line break

<hr> Defines a horizontal line

Matching tags

These require an ending tag - e.g. <i>italic text</i>

<a> Defines an anchor

<b> Defines bold text

<big> Defines big text

<blockquote> Defines a long quotation

<caption> Defines a table caption

<cite> Defines a citation

<code> Defines computer code text

<em> Defines emphasized text

<fieldset> Defines a border around elements in a form

<h1> This is heading 1

<h2> This is heading 2

<h3> This is heading 3

<h4> This is heading 4

<h5> This is heading 5

<h6> This is heading 6

<i> Defines italic text

<p> Defines a paragraph

<pre> Defines preformatted text

<q> Defines a short quotation

<samp> Defines sample computer code text

<small> Defines small text

<span> Defines a section in a document

<s> Defines strikethrough text

<strike> Defines strikethrough text

<strong> Defines strong text

<sub> Defines subscripted text

<sup> Defines superscripted text

<u> Defines underlined text

Dr. Dobb's encourages readers to engage in spirited, healthy debate, including taking us to task. However, Dr. Dobb's moderates all comments posted to our site, and reserves the right to modify or remove any content that it determines to be derogatory, offensive, inflammatory, vulgar, irrelevant/off-topic, racist or obvious marketing or spam. Dr. Dobb's further reserves the right to disable the profile of any commenter participating in said activities.

 
Disqus Tips To upload an avatar photo, first complete your Disqus profile. | View the list of supported HTML tags you can use to style comments. | Please read our commenting policy.
 

Video