OpCodes Class (System.Reflection.Emit)

Imports System
Imports System.Threading
Imports System.Reflection
Imports System.Reflection.Emit

 _

Class EmitWriteLineDemo


   Public Shared Function CreateDynamicType() As Type

      Dim ctorParams() As Type = {GetType(Integer), GetType(Integer)}

      Dim myDomain As AppDomain = Thread.GetDomain()
      Dim myAsmName As New AssemblyName()
      myAsmName.Name = "MyDynamicAssembly"

      Dim myAsmBuilder As AssemblyBuilder = myDomain.DefineDynamicAssembly(myAsmName, AssemblyBuilderAccess.RunAndSave)

      Dim pointModule As ModuleBuilder = myAsmBuilder.DefineDynamicModule("PointModule", "Point.dll")

      Dim pointTypeBld As TypeBuilder = pointModule.DefineType("Point", _
							       TypeAttributes.Public)

      Dim xField As FieldBuilder = pointTypeBld.DefineField("x", _
							    GetType(Integer), _
							    FieldAttributes.Public)
      Dim yField As FieldBuilder = pointTypeBld.DefineField("y", _
							    GetType(Integer), _
						 	    FieldAttributes.Public)


      Dim objType As Type = Type.GetType("System.Object")
      Dim objCtor As ConstructorInfo = objType.GetConstructor(New Type(){})

      Dim pointCtor As ConstructorBuilder = pointTypeBld.DefineConstructor( _
							 MethodAttributes.Public, _
							 CallingConventions.Standard, _
							 ctorParams)
      Dim ctorIL As ILGenerator = pointCtor.GetILGenerator()


      ' First, you build the constructor.

      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.Ret)

      '  Now, you'll build a method to output some information on the
      ' inside your dynamic class. This method will have the following
      ' definition in C#:
      '  Public Sub WritePoint() 

      Dim writeStrMthd As MethodBuilder = pointTypeBld.DefineMethod("WritePoint", _
								    MethodAttributes.Public, _
								    Nothing, Nothing)

      Dim writeStrIL As ILGenerator = writeStrMthd.GetILGenerator()

      ' The below ILGenerator created demonstrates a few ways to create
      ' string output through STDIN. 
      ' ILGenerator.EmitWriteLine(string) will generate a ldstr and a 
      ' call to WriteLine for you.

      writeStrIL.EmitWriteLine("The value of this current instance is:")

      ' Here, you will do the hard work yourself. First, you need to create
      ' the string we will be passing and obtain the correct WriteLine overload
      ' for said string. In the below case, you are substituting in two values,
      ' so the chosen overload is Console.WriteLine(string, object, object).

      Dim inStr As [String] = "({0}, {1})"
      Dim wlParams() As Type = {GetType(String), GetType(Object), GetType(Object)}

      ' We need the MethodInfo to pass into EmitCall later.

      Dim writeLineMI As MethodInfo = GetType(Console).GetMethod("WriteLine", wlParams)

      ' Push the string with the substitutions onto the stack.
      ' This is the first argument for WriteLine - the string one. 

      writeStrIL.Emit(OpCodes.Ldstr, inStr)

      ' Since the second argument is an object, and it corresponds to
      ' to the substitution for the value of our integer field, you 
      ' need to box that field to an object. First, push a reference
      ' to the current instance, and then push the value stored in
      ' field 'x'. We need the reference to the current instance (stored
      ' in local argument index 0) so Ldfld can load from the correct
      ' instance (this one).

      writeStrIL.Emit(OpCodes.Ldarg_0)
      writeStrIL.Emit(OpCodes.Ldfld, xField)

      ' Now, we execute the box opcode, which pops the value of field 'x',
      ' returning a reference to the integer value boxed as an object.

      writeStrIL.Emit(OpCodes.Box, GetType(Integer))

      ' Atop the stack, you'll find our string inStr, followed by a reference
      ' to the boxed value of 'x'. Now, you need to likewise box field 'y'.

      writeStrIL.Emit(OpCodes.Ldarg_0)
      writeStrIL.Emit(OpCodes.Ldfld, yField)
      writeStrIL.Emit(OpCodes.Box, GetType(Integer))

      ' Now, you have all of the arguments for your call to
      ' Console.WriteLine(string, object, object) atop the stack:
      ' the string InStr, a reference to the boxed value of 'x', and
      ' a reference to the boxed value of 'y'.
      ' Call Console.WriteLine(string, object, object) with EmitCall.

      writeStrIL.EmitCall(OpCodes.Call, writeLineMI, Nothing)

      ' Lastly, EmitWriteLine can also output the value of a field
      ' using the overload EmitWriteLine(FieldInfo).

      writeStrIL.EmitWriteLine("The value of 'x' is:")
      writeStrIL.EmitWriteLine(xField)
      writeStrIL.EmitWriteLine("The value of 'y' is:")
      writeStrIL.EmitWriteLine(yField)

      ' Since we return no value (void), the the ret opcode will not
      ' return the top stack value.

      writeStrIL.Emit(OpCodes.Ret)

      Return pointTypeBld.CreateType()

   End Function 'CreateDynamicType


   Public Shared Sub Main()

      Dim ctorParams(1) As Object

      Console.Write("Enter a integer value for X: ")
      Dim myX As String = Console.ReadLine()
      Console.Write("Enter a integer value for Y: ")
      Dim myY As String = Console.ReadLine()

      Console.WriteLine("---")

      ctorParams(0) = Convert.ToInt32(myX)
      ctorParams(1) = Convert.ToInt32(myY)

      Dim ptType As Type = CreateDynamicType()

      Dim ptInstance As Object = Activator.CreateInstance(ptType, ctorParams)

      ptType.InvokeMember("WritePoint", _
			  BindingFlags.InvokeMethod, _
			  Nothing, ptInstance, Nothing)

   End Sub 'Main

End Class 'EmitWriteLineDemo

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

class EmitWriteLineDemo {

   public static Type CreateDynamicType() {       
       Type[] ctorParams = new Type[] {typeof(int),
				   typeof(int)};
 	
       AppDomain myDomain = Thread.GetDomain();
       AssemblyName myAsmName = new AssemblyName();
       myAsmName.Name = "MyDynamicAssembly";

       AssemblyBuilder myAsmBuilder = myDomain.DefineDynamicAssembly(
				      myAsmName, 
				      AssemblyBuilderAccess.Run);

       ModuleBuilder pointModule = myAsmBuilder.DefineDynamicModule("PointModule",
								    "Point.dll");

       TypeBuilder pointTypeBld = pointModule.DefineType("Point",
					              TypeAttributes.Public);

       FieldBuilder xField = pointTypeBld.DefineField("x", typeof(int),
                                                      FieldAttributes.Public);
       FieldBuilder yField = pointTypeBld.DefineField("y", typeof(int), 
                                                      FieldAttributes.Public);


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

       ConstructorBuilder pointCtor = pointTypeBld.DefineConstructor(
 				                   MethodAttributes.Public,
				                   CallingConventions.Standard,
				                   ctorParams);
       ILGenerator ctorIL = pointCtor.GetILGenerator();


       // First, you build the constructor.
       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.Ret); 

       //  Now, you'll build a method to output some information on the
       // inside your dynamic class. This method will have the following
       // definition in C#:
	//  public void WritePoint()

       MethodBuilder writeStrMthd = pointTypeBld.DefineMethod(
        		                     "WritePoint", 
				             MethodAttributes.Public,
                                             typeof(void), 
                                             null);


       ILGenerator writeStrIL = writeStrMthd.GetILGenerator();

       // The below ILGenerator created demonstrates a few ways to create
       // string output through STDIN. 

       // ILGenerator.EmitWriteLine(string) will generate a ldstr and a 
       // call to WriteLine for you.

       writeStrIL.EmitWriteLine("The value of this current instance is:");

       // Here, you will do the hard work yourself. First, you need to create
       // the string we will be passing and obtain the correct WriteLine overload
       // for said string. In the below case, you are substituting in two values,
       // so the chosen overload is Console.WriteLine(string, object, object).

       String inStr = "({0}, {1})";
       Type[] wlParams = new Type[] {typeof(string),
				     typeof(object),
				     typeof(object)};

       // We need the MethodInfo to pass into EmitCall later.

       MethodInfo writeLineMI = typeof(Console).GetMethod(
					        "WriteLine",
						wlParams);

       // Push the string with the substitutions onto the stack.
       // This is the first argument for WriteLine - the string one. 

       writeStrIL.Emit(OpCodes.Ldstr, inStr);

       // Since the second argument is an object, and it corresponds to
       // to the substitution for the value of our integer field, you 
       // need to box that field to an object. First, push a reference
       // to the current instance, and then push the value stored in
       // field 'x'. We need the reference to the current instance (stored
       // in local argument index 0) so Ldfld can load from the correct
       // instance (this one).

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

       // Now, we execute the box opcode, which pops the value of field 'x',
       // returning a reference to the integer value boxed as an object.

       writeStrIL.Emit(OpCodes.Box, typeof(int));

       // Atop the stack, you'll find our string inStr, followed by a reference
       // to the boxed value of 'x'. Now, you need to likewise box field 'y'.

       writeStrIL.Emit(OpCodes.Ldarg_0);
       writeStrIL.Emit(OpCodes.Ldfld, yField);
       writeStrIL.Emit(OpCodes.Box, typeof(int));

       // Now, you have all of the arguments for your call to
       // Console.WriteLine(string, object, object) atop the stack:
       // the string InStr, a reference to the boxed value of 'x', and
       // a reference to the boxed value of 'y'.

       // Call Console.WriteLine(string, object, object) with EmitCall.

       writeStrIL.EmitCall(OpCodes.Call, writeLineMI, null);

       // Lastly, EmitWriteLine can also output the value of a field
       // using the overload EmitWriteLine(FieldInfo).

       writeStrIL.EmitWriteLine("The value of 'x' is:");
       writeStrIL.EmitWriteLine(xField);
       writeStrIL.EmitWriteLine("The value of 'y' is:");
       writeStrIL.EmitWriteLine(yField);

       // Since we return no value (void), the the ret opcode will not
       // return the top stack value.

       writeStrIL.Emit(OpCodes.Ret);

       return pointTypeBld.CreateType();

   }

   public static void Main() {

      object[] ctorParams = new object[2];

      Console.Write("Enter a integer value for X: "); 
      string myX = Console.ReadLine();
      Console.Write("Enter a integer value for Y: "); 
      string myY = Console.ReadLine();

      Console.WriteLine("---");

      ctorParams[0] = Convert.ToInt32(myX);
      ctorParams[1] = Convert.ToInt32(myY);

      Type ptType = CreateDynamicType();

      object ptInstance = Activator.CreateInstance(ptType, ctorParams);
      ptType.InvokeMember("WritePoint",
			  BindingFlags.InvokeMethod,
			  null,
			  ptInstance,
			  new object[0]);
   }
}

using namespace System;
using namespace System::Threading;
using namespace System::Reflection;
using namespace System::Reflection::Emit;
Type^ CreateDynamicType()
{
   array<Type^>^ctorParams = {int::typeid,int::typeid};
   AppDomain^ myDomain = Thread::GetDomain();
   AssemblyName^ myAsmName = gcnew AssemblyName;
   myAsmName->Name = "MyDynamicAssembly";
   AssemblyBuilder^ myAsmBuilder = myDomain->DefineDynamicAssembly( myAsmName, AssemblyBuilderAccess::Run );
   ModuleBuilder^ pointModule = myAsmBuilder->DefineDynamicModule( "PointModule", "Point.dll" );
   TypeBuilder^ pointTypeBld = pointModule->DefineType( "Point", TypeAttributes::Public );
   FieldBuilder^ xField = pointTypeBld->DefineField( "x", int::typeid, FieldAttributes::Public );
   FieldBuilder^ yField = pointTypeBld->DefineField( "y", int::typeid, FieldAttributes::Public );
   Type^ objType = Type::GetType( "System.Object" );
   ConstructorInfo^ objCtor = objType->GetConstructor( gcnew array<Type^>(0) );
   ConstructorBuilder^ pointCtor = pointTypeBld->DefineConstructor( MethodAttributes::Public, CallingConventions::Standard, ctorParams );
   ILGenerator^ ctorIL = pointCtor->GetILGenerator();

   // First, you build the constructor.
   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::Ret );

   //  Now, you'll build a method to output some information on the
   // inside your dynamic class. This method will have the following
   // definition in C#:
   //  public void WritePoint()
   MethodBuilder^ writeStrMthd = pointTypeBld->DefineMethod( "WritePoint", MethodAttributes::Public, void::typeid, nullptr );
   ILGenerator^ writeStrIL = writeStrMthd->GetILGenerator();

   // The below ILGenerator created demonstrates a few ways to create
   // String* output through STDIN.
   // ILGenerator::EmitWriteLine(String*) will generate a ldstr and a
   // call to WriteLine for you.
   writeStrIL->EmitWriteLine( "The value of this current instance is:" );

   // Here, you will do the hard work yourself. First, you need to create
   // the String* we will be passing and obtain the correct WriteLine overload
   // for said String*. In the below case, you are substituting in two values,
   // so the chosen overload is Console::WriteLine(String*, Object*, Object*).
   String^ inStr = "( {0}, {1})";
   array<Type^>^wlParams = {String::typeid,Object::typeid,Object::typeid};

   // We need the MethodInfo to pass into EmitCall later.
   MethodInfo^ writeLineMI = Console::typeid->GetMethod( "WriteLine", wlParams );

   // Push the String* with the substitutions onto the stack.
   // This is the first argument for WriteLine - the String* one.
   writeStrIL->Emit( OpCodes::Ldstr, inStr );

   // Since the second argument is an Object*, and it corresponds to
   // to the substitution for the value of our integer field, you
   // need to box that field to an Object*. First, push a reference
   // to the current instance, and then push the value stored in
   // field 'x'. We need the reference to the current instance (stored
   // in local argument index 0) so Ldfld can load from the correct
   // instance (this one).
   writeStrIL->Emit( OpCodes::Ldarg_0 );
   writeStrIL->Emit( OpCodes::Ldfld, xField );

   // Now, we execute the box opcode, which pops the value of field 'x',
   // returning a reference to the integer value boxed as an Object*.
   writeStrIL->Emit( OpCodes::Box, int::typeid );

   // Atop the stack, you'll find our String* inStr, followed by a reference
   // to the boxed value of 'x'. Now, you need to likewise box field 'y'.
   writeStrIL->Emit( OpCodes::Ldarg_0 );
   writeStrIL->Emit( OpCodes::Ldfld, yField );
   writeStrIL->Emit( OpCodes::Box, int::typeid );

   // Now, you have all of the arguments for your call to
   // Console::WriteLine(String*, Object*, Object*) atop the stack:
   // the String* InStr, a reference to the boxed value of 'x', and
   // a reference to the boxed value of 'y'.
   // Call Console::WriteLine(String*, Object*, Object*) with EmitCall.
   writeStrIL->EmitCall( OpCodes::Call, writeLineMI, nullptr );

   // Lastly, EmitWriteLine can also output the value of a field
   // using the overload EmitWriteLine(FieldInfo).
   writeStrIL->EmitWriteLine( "The value of 'x' is:" );
   writeStrIL->EmitWriteLine( xField );
   writeStrIL->EmitWriteLine( "The value of 'y' is:" );
   writeStrIL->EmitWriteLine( yField );

   // Since we return no value (void), the the ret opcode will not
   // return the top stack value.
   writeStrIL->Emit( OpCodes::Ret );
   return pointTypeBld->CreateType();
}

int main()
{
   array<Object^>^ctorParams = gcnew array<Object^>(2);
   Console::Write( "Enter a integer value for X: " );
   String^ myX = Console::ReadLine();
   Console::Write( "Enter a integer value for Y: " );
   String^ myY = Console::ReadLine();
   Console::WriteLine( "---" );
   ctorParams[ 0 ] = Convert::ToInt32( myX );
   ctorParams[ 1 ] = Convert::ToInt32( myY );
   Type^ ptType = CreateDynamicType();
   Object^ ptInstance = Activator::CreateInstance( ptType, ctorParams );
   ptType->InvokeMember( "WritePoint", BindingFlags::InvokeMethod, nullptr, ptInstance, gcnew array<Object^>(0) );
}