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MethodBuilder.GetILGenerator Method

Returns an ILGenerator for this method with a default Microsoft intermediate language (MSIL) stream size of 64 bytes.

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

public ILGenerator GetILGenerator()

Return Value

Type: System.Reflection.Emit.ILGenerator
Returns an ILGenerator object for this method.

ExceptionCondition
InvalidOperationException

The method should not have a body because of its MethodAttributes or MethodImplAttributes flags, for example because it has the MethodAttributes.PinvokeImpl flag.

-or-

The method is a generic method, but not a generic method definition. That is, the IsGenericMethod property is true, but the IsGenericMethodDefinition property is false.

The code sample below demonstrates the contextual usage of the GetILGenerator method, creating and emitting a dynamic assembly that will calculate the dot product of two points in 3D space.


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


class TestILGenerator {

  	public static Type DynamicDotProductGen() {
	  
	   Type ivType = null;
	   Type[] ctorParams = new Type[] { typeof(int),
		               		    typeof(int),
					    typeof(int)};
 	
	   AppDomain myDomain = Thread.GetDomain();
	   AssemblyName myAsmName = new AssemblyName();
	   myAsmName.Name = "IntVectorAsm";
	
	   AssemblyBuilder myAsmBuilder = myDomain.DefineDynamicAssembly(
					  myAsmName, 
					  AssemblyBuilderAccess.RunAndSave);

   	   ModuleBuilder IntVectorModule = myAsmBuilder.DefineDynamicModule("IntVectorModule",
									    "Vector.dll");

	   TypeBuilder ivTypeBld = IntVectorModule.DefineType("IntVector",
						              TypeAttributes.Public);

	   FieldBuilder xField = ivTypeBld.DefineField("x", typeof(int),
                                                       FieldAttributes.Private);
	   FieldBuilder yField = ivTypeBld.DefineField("y", typeof(int), 
                                                       FieldAttributes.Private);
	   FieldBuilder zField = ivTypeBld.DefineField("z", typeof(int),
                                                       FieldAttributes.Private);


           Type objType = Type.GetType("System.Object"); 
           ConstructorInfo objCtor = objType.GetConstructor(new Type[0]);

	   ConstructorBuilder ivCtor = ivTypeBld.DefineConstructor(
					  MethodAttributes.Public,
					  CallingConventions.Standard,
					  ctorParams);
	   ILGenerator ctorIL = ivCtor.GetILGenerator();
           ctorIL.Emit(OpCodes.Ldarg_0);
           ctorIL.Emit(OpCodes.Call, objCtor);
           ctorIL.Emit(OpCodes.Ldarg_0);
           ctorIL.Emit(OpCodes.Ldarg_1);
           ctorIL.Emit(OpCodes.Stfld, xField); 
           ctorIL.Emit(OpCodes.Ldarg_0);
           ctorIL.Emit(OpCodes.Ldarg_2);
           ctorIL.Emit(OpCodes.Stfld, yField); 
           ctorIL.Emit(OpCodes.Ldarg_0);
           ctorIL.Emit(OpCodes.Ldarg_3);
           ctorIL.Emit(OpCodes.Stfld, zField); 
	   ctorIL.Emit(OpCodes.Ret); 


	   // This method will find the dot product of the stored vector 
	   // with another.

	   Type[] dpParams = new Type[] { ivTypeBld };

           // Here, you create a MethodBuilder containing the 
	   // name, the attributes (public, static, private, and so on), 
	   // the return type (int, in this case), and a array of Type 
	   // indicating the type of each parameter. Since the sole parameter 
	   // is a IntVector, the very class you're creating, you will 
	   // pass in the TypeBuilder (which is derived from Type) instead of  
	   // a Type object for IntVector, avoiding an exception.  

	   // -- This method would be declared in C# as: 
	   //    public int DotProduct(IntVector aVector)

           MethodBuilder dotProductMthd = ivTypeBld.DefineMethod(
	    		                  "DotProduct", 
				          MethodAttributes.Public,
                                          typeof(int), 
                                          dpParams);

	   // A ILGenerator can now be spawned, attached to the MethodBuilder.

	   ILGenerator mthdIL = dotProductMthd.GetILGenerator();
	   
 	   // Here's the body of our function, in MSIL form. We're going to find the 
	   // "dot product" of the current vector instance with the passed vector 
	   // instance. For reference purposes, the equation is: 
	   // (x1 * x2) + (y1 * y2) + (z1 * z2) = the dot product 

	   // First, you'll load the reference to the current instance "this" 
	   // stored in argument 0 (ldarg.0) onto the stack. Ldfld, the subsequent 
	   // instruction, will pop the reference off the stack and look up the 
	   // field "x", specified by the FieldInfo token "xField".

	   mthdIL.Emit(OpCodes.Ldarg_0);
	   mthdIL.Emit(OpCodes.Ldfld, xField);

	   // That completed, the value stored at field "x" is now atop the stack.
	   // Now, you'll do the same for the object reference we passed as a 
	   // parameter, stored in argument 1 (ldarg.1). After Ldfld executed, 
	   // you'll have the value stored in field "x" for the passed instance
	   // atop the stack.

	   mthdIL.Emit(OpCodes.Ldarg_1);
	   mthdIL.Emit(OpCodes.Ldfld, xField);

           // There will now be two values atop the stack - the "x" value for the
	   // current vector instance, and the "x" value for the passed instance.
	   // You'll now multiply them, and push the result onto the evaluation stack.

	   mthdIL.Emit(OpCodes.Mul_Ovf_Un);

	   // Now, repeat this for the "y" fields of both vectors.

	   mthdIL.Emit(OpCodes.Ldarg_0);
	   mthdIL.Emit(OpCodes.Ldfld, yField);
	   mthdIL.Emit(OpCodes.Ldarg_1);
	   mthdIL.Emit(OpCodes.Ldfld, yField);
	   mthdIL.Emit(OpCodes.Mul_Ovf_Un);

	   // At this time, the results of both multiplications should be atop 
	   // the stack. You'll now add them and push the result onto the stack.

	   mthdIL.Emit(OpCodes.Add_Ovf_Un);

	   // Multiply both "z" field and push the result onto the stack.
	   mthdIL.Emit(OpCodes.Ldarg_0);
	   mthdIL.Emit(OpCodes.Ldfld, zField);
	   mthdIL.Emit(OpCodes.Ldarg_1);
	   mthdIL.Emit(OpCodes.Ldfld, zField);
	   mthdIL.Emit(OpCodes.Mul_Ovf_Un);

	   // Finally, add the result of multiplying the "z" fields with the
	   // result of the earlier addition, and push the result - the dot product - 
	   // onto the stack.
	   mthdIL.Emit(OpCodes.Add_Ovf_Un);

	   // The "ret" opcode will pop the last value from the stack and return it
	   // to the calling method. You're all done!

	   mthdIL.Emit(OpCodes.Ret);


 	   ivType = ivTypeBld.CreateType();

	   return ivType;

 	}

	public static void Main() {
	
	   Type IVType = null;
           object aVector1 = null;
           object aVector2 = null;
	   Type[] aVtypes = new Type[] {typeof(int), typeof(int), typeof(int)};
           object[] aVargs1 = new object[] {10, 10, 10};
           object[] aVargs2 = new object[] {20, 20, 20};
	
	   // Call the  method to build our dynamic class.

	   IVType = DynamicDotProductGen();

           Console.WriteLine("---");

	   ConstructorInfo myDTctor = IVType.GetConstructor(aVtypes);
	   aVector1 = myDTctor.Invoke(aVargs1);
	   aVector2 = myDTctor.Invoke(aVargs2);

	   object[] passMe = new object[1];
           passMe[0] = (object)aVector2; 

	   Console.WriteLine("(10, 10, 10) . (20, 20, 20) = {0}",
			     IVType.InvokeMember("DotProduct",
						  BindingFlags.InvokeMethod,
						  null,
						  aVector1,
						  passMe));

	    

	   // +++ OUTPUT +++ 
	   // --- 
	   // (10, 10, 10) . (20, 20, 20) = 600 
	    
	}

}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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