This documentation is archived and is not being maintained.

MethodBuilder.CreateMethodBody Method

Creates the body of the method using a supplied byte array of Microsoft intermediate language (MSIL) instructions.

Namespace:  System.Reflection.Emit
Assembly:  mscorlib (in mscorlib.dll)

public void CreateMethodBody(
	byte[] il,
	int count


Type: System.Byte[]
An array containing valid MSIL instructions. If this parameter is null, the method's body is cleared.
Type: System.Int32
The number of valid bytes in the MSIL array. This value is ignored if MSIL is null.


The count is not within the range of indexes of the supplied MSIL instruction array and il is not null.


The containing type was previously created using CreateType.


This method was called previously on this MethodBuilder with an il argument that was not null.


For the current method, the IsGenericMethod property is true, but the IsGenericMethodDefinition property is false.

This method creates the method's body from il, an array containing MSIL instructions as opcodes. The number of bytes of valid MSIL is given by count.


This is currently not fully supported. The user cannot supply the location of token fix ups and exception handlers.

In the example provided below, a simple method that adds two integers is generated via opcode using CreateMethodBody.

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

class MethodBodyDemo {
// This class will demonstrate how to create a method body using 
// the MethodBuilder.CreateMethodBody(byte[], int) method.

   public static Type BuildDynType() {

  	Type addType = null;

    	AppDomain currentDom = Thread.GetDomain();

        AssemblyName myAsmName = new AssemblyName();
	myAsmName.Name = "MyDynamicAssembly";

        AssemblyBuilder myAsmBldr = currentDom.DefineDynamicAssembly(

        // The dynamic assembly space has been created.  Next, create a module
        // within it.  The type Point will be reflected into this module.

	ModuleBuilder myModuleBldr = myAsmBldr.DefineDynamicModule("MyModule");

	TypeBuilder myTypeBldr =  myModuleBldr.DefineType("Adder");

        MethodBuilder myMthdBldr = myTypeBldr.DefineMethod("DoAdd",
							    MethodAttributes.Public |
							    new Type[] 
							    {typeof(int), typeof(int)});
        // Build the array of Bytes holding the MSIL instructions.

        byte[] ILcodes = new byte[] {
          0x02,   /* 02h is the opcode for ldarg.0 */
	  0x03,   /* 03h is the opcode for ldarg.1 */
	  0x58,   /* 58h is the opcode for add     */
	  0x2A    /* 2Ah is the opcode for ret     */
	myMthdBldr.CreateMethodBody(ILcodes, ILcodes.Length);

        addType = myTypeBldr.CreateType();

	return addType;

   public static void Main() {

	Type myType = BuildDynType(); 
	Console.Write("Enter the first integer to add: "); 
        int aVal = Convert.ToInt32(Console.ReadLine());

     	Console.Write("Enter the second integer to add: ");
     	int bVal = Convert.ToInt32(Console.ReadLine());

     	object adderInst = Activator.CreateInstance(myType, new object[0]); 

	Console.WriteLine("The value of adding {0} to {1} is: {2}.",
			   aVal, bVal,	
			  		       new object[] {aVal, bVal})); 


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.