ILGenerator.Emit ILGenerator.Emit ILGenerator.Emit Method

Definition

Puts an instruction onto the Microsoft Intermediate Language (MSIL) stream for the just-in-time (JIT) compiler.

Overloads

Emit(OpCode, Type) Emit(OpCode, Type) Emit(OpCode, Type)

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream followed by the metadata token for the given type.

Emit(OpCode, String) Emit(OpCode, String) Emit(OpCode, String)

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream followed by the metadata token for the given string.

Emit(OpCode, Single) Emit(OpCode, Single) Emit(OpCode, Single)

Puts the specified instruction and numerical argument onto the Microsoft intermediate language (MSIL) stream of instructions.

Emit(OpCode, SByte) Emit(OpCode, SByte) Emit(OpCode, SByte)

Puts the specified instruction and character argument onto the Microsoft intermediate language (MSIL) stream of instructions.

Emit(OpCode, FieldInfo) Emit(OpCode, FieldInfo) Emit(OpCode, FieldInfo)

Puts the specified instruction and metadata token for the specified field onto the Microsoft intermediate language (MSIL) stream of instructions.

Emit(OpCode, SignatureHelper) Emit(OpCode, SignatureHelper) Emit(OpCode, SignatureHelper)

Puts the specified instruction and a signature token onto the Microsoft intermediate language (MSIL) stream of instructions.

Emit(OpCode, LocalBuilder) Emit(OpCode, LocalBuilder) Emit(OpCode, LocalBuilder)

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream followed by the index of the given local variable.

Emit(OpCode, Label[]) Emit(OpCode, Label[]) Emit(OpCode, Label[])

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream and leaves space to include a label when fixes are done.

Emit(OpCode, MethodInfo) Emit(OpCode, MethodInfo) Emit(OpCode, MethodInfo)

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream followed by the metadata token for the given method.

Emit(OpCode, ConstructorInfo) Emit(OpCode, ConstructorInfo) Emit(OpCode, ConstructorInfo)

Puts the specified instruction and metadata token for the specified constructor onto the Microsoft intermediate language (MSIL) stream of instructions.

Emit(OpCode, Int64) Emit(OpCode, Int64) Emit(OpCode, Int64)

Puts the specified instruction and numerical argument onto the Microsoft intermediate language (MSIL) stream of instructions.

Emit(OpCode, Int32) Emit(OpCode, Int32) Emit(OpCode, Int32)

Puts the specified instruction and numerical argument onto the Microsoft intermediate language (MSIL) stream of instructions.

Emit(OpCode, Int16) Emit(OpCode, Int16) Emit(OpCode, Int16)

Puts the specified instruction and numerical argument onto the Microsoft intermediate language (MSIL) stream of instructions.

Emit(OpCode, Double) Emit(OpCode, Double) Emit(OpCode, Double)

Puts the specified instruction and numerical argument onto the Microsoft intermediate language (MSIL) stream of instructions.

Emit(OpCode, Byte) Emit(OpCode, Byte) Emit(OpCode, Byte)

Puts the specified instruction and character argument onto the Microsoft intermediate language (MSIL) stream of instructions.

Emit(OpCode) Emit(OpCode) Emit(OpCode)

Puts the specified instruction onto the stream of instructions.

Emit(OpCode, Label) Emit(OpCode, Label) Emit(OpCode, Label)

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream and leaves space to include a label when fixes are done.

Emit(OpCode, Type) Emit(OpCode, Type) Emit(OpCode, Type)

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream followed by the metadata token for the given type.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, Type ^ cls);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, Type cls);
abstract member Emit : System.Reflection.Emit.OpCode * Type -> unit
override this.Emit : System.Reflection.Emit.OpCode * Type -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be put onto the stream.

cls
Type Type Type

A Type.

Exceptions

Remarks

The instruction values are defined in the OpCodes enumeration. The location of cls is recorded so that the token can be patched if necessary when persisting the module to a portable executable (PE) file.

Emit(OpCode, String) Emit(OpCode, String) Emit(OpCode, String)

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream followed by the metadata token for the given string.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, System::String ^ str);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, string str);
abstract member Emit : System.Reflection.Emit.OpCode * string -> unit
override this.Emit : System.Reflection.Emit.OpCode * string -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be emitted onto the stream.

str
String String String

The String to be emitted.

Remarks

The instruction values are defined in the OpCodes enumeration. The location of str is recorded for future fixups if the module is persisted to a portable executable (PE) file.

Emit(OpCode, Single) Emit(OpCode, Single) Emit(OpCode, Single)

Puts the specified instruction and numerical argument onto the Microsoft intermediate language (MSIL) stream of instructions.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, float arg);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, float arg);
abstract member Emit : System.Reflection.Emit.OpCode * single -> unit
override this.Emit : System.Reflection.Emit.OpCode * single -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be put onto the stream.

arg
Single Single Single

The Single argument pushed onto the stream immediately after the instruction.

Remarks

The instruction values are defined in the OpCodes enumeration.

Emit(OpCode, SByte) Emit(OpCode, SByte) Emit(OpCode, SByte)

Important

This API is not CLS-compliant.

Puts the specified instruction and character argument onto the Microsoft intermediate language (MSIL) stream of instructions.

public:
 void Emit(System::Reflection::Emit::OpCode opcode, System::SByte arg);
[System.CLSCompliant(false)]
public void Emit (System.Reflection.Emit.OpCode opcode, sbyte arg);
member this.Emit : System.Reflection.Emit.OpCode * sbyte -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be put onto the stream.

arg
SByte SByte SByte

The character argument pushed onto the stream immediately after the instruction.

Remarks

The instruction values are defined in the OpCodes enumeration.

Emit(OpCode, FieldInfo) Emit(OpCode, FieldInfo) Emit(OpCode, FieldInfo)

Puts the specified instruction and metadata token for the specified field onto the Microsoft intermediate language (MSIL) stream of instructions.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, System::Reflection::FieldInfo ^ field);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, System.Reflection.FieldInfo field);
abstract member Emit : System.Reflection.Emit.OpCode * System.Reflection.FieldInfo -> unit
override this.Emit : System.Reflection.Emit.OpCode * System.Reflection.FieldInfo -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be emitted onto the stream.

field
FieldInfo FieldInfo FieldInfo

A FieldInfo representing a field.

Remarks

The instruction values are defined in the OpCodes enumeration. The location of field is recorded so that the instruction stream can be patched if necessary when persisting the module to a portable executable (PE) file.

Emit(OpCode, SignatureHelper) Emit(OpCode, SignatureHelper) Emit(OpCode, SignatureHelper)

Puts the specified instruction and a signature token onto the Microsoft intermediate language (MSIL) stream of instructions.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, System::Reflection::Emit::SignatureHelper ^ signature);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, System.Reflection.Emit.SignatureHelper signature);
abstract member Emit : System.Reflection.Emit.OpCode * System.Reflection.Emit.SignatureHelper -> unit
override this.Emit : System.Reflection.Emit.OpCode * System.Reflection.Emit.SignatureHelper -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be emitted onto the stream.

signature
SignatureHelper SignatureHelper SignatureHelper

A helper for constructing a signature token.

Exceptions

Remarks

The instruction values are defined in the OpCodes enumeration.

Emit(OpCode, LocalBuilder) Emit(OpCode, LocalBuilder) Emit(OpCode, LocalBuilder)

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream followed by the index of the given local variable.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, System::Reflection::Emit::LocalBuilder ^ local);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, System.Reflection.Emit.LocalBuilder local);
abstract member Emit : System.Reflection.Emit.OpCode * System.Reflection.Emit.LocalBuilder -> unit
override this.Emit : System.Reflection.Emit.OpCode * System.Reflection.Emit.LocalBuilder -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be emitted onto the stream.

local
LocalBuilder LocalBuilder LocalBuilder

A local variable.

Exceptions

The parent method of the local parameter does not match the method associated with this ILGenerator.

opcode is a single-byte instruction, and local represents a local variable with an index greater than Byte.MaxValue.

Remarks

The instruction values are defined in the OpCodes enumeration.

Emit(OpCode, Label[]) Emit(OpCode, Label[]) Emit(OpCode, Label[])

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream and leaves space to include a label when fixes are done.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, cli::array <System::Reflection::Emit::Label> ^ labels);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, System.Reflection.Emit.Label[] labels);
abstract member Emit : System.Reflection.Emit.OpCode * System.Reflection.Emit.Label[] -> unit
override this.Emit : System.Reflection.Emit.OpCode * System.Reflection.Emit.Label[] -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be emitted onto the stream.

labels
Label[]

The array of label objects to which to branch from this location. All of the labels will be used.

Exceptions

con is null. This exception is new in the .NET Framework 4.

Examples

The code sample below illustrates the creation of a dynamic method with a jump table. The jump table is built using an array of Label.

using namespace System;
using namespace System::Threading;
using namespace System::Reflection;
using namespace System::Reflection::Emit;
Type^ BuildMyType()
{
   AppDomain^ myDomain = Thread::GetDomain();
   AssemblyName^ myAsmName = gcnew AssemblyName;
   myAsmName->Name = "MyDynamicAssembly";
   AssemblyBuilder^ myAsmBuilder = myDomain->DefineDynamicAssembly( myAsmName, AssemblyBuilderAccess::Run );
   ModuleBuilder^ myModBuilder = myAsmBuilder->DefineDynamicModule( "MyJumpTableDemo" );
   TypeBuilder^ myTypeBuilder = myModBuilder->DefineType( "JumpTableDemo", TypeAttributes::Public );
   array<Type^>^temp0 = {int::typeid};
   MethodBuilder^ myMthdBuilder = myTypeBuilder->DefineMethod( "SwitchMe", static_cast<MethodAttributes>(MethodAttributes::Public | MethodAttributes::Static), String::typeid, temp0 );
   ILGenerator^ myIL = myMthdBuilder->GetILGenerator();
   Label defaultCase = myIL->DefineLabel();
   Label endOfMethod = myIL->DefineLabel();
   
   // We are initializing our jump table. Note that the labels
   // will be placed later using the MarkLabel method.
   array<Label>^jumpTable = gcnew array<Label>(5);
   jumpTable[ 0 ] = myIL->DefineLabel();
   jumpTable[ 1 ] = myIL->DefineLabel();
   jumpTable[ 2 ] = myIL->DefineLabel();
   jumpTable[ 3 ] = myIL->DefineLabel();
   jumpTable[ 4 ] = myIL->DefineLabel();
   
   // arg0, the number we passed, is pushed onto the stack.
   // In this case, due to the design of the code sample,
   // the value pushed onto the stack happens to match the
   // index of the label (in IL terms, the index of the offset
   // in the jump table). If this is not the case, such as
   // when switching based on non-integer values, rules for the correspondence
   // between the possible case values and each index of the offsets
   // must be established outside of the ILGenerator::Emit calls,
   // much as a compiler would.
   myIL->Emit( OpCodes::Ldarg_0 );
   myIL->Emit( OpCodes::Switch, jumpTable );
   
   // Branch on default case
   myIL->Emit( OpCodes::Br_S, defaultCase );
   
   // Case arg0 = 0
   myIL->MarkLabel( jumpTable[ 0 ] );
   myIL->Emit( OpCodes::Ldstr, "are no bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 1
   myIL->MarkLabel( jumpTable[ 1 ] );
   myIL->Emit( OpCodes::Ldstr, "is one banana" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 2
   myIL->MarkLabel( jumpTable[ 2 ] );
   myIL->Emit( OpCodes::Ldstr, "are two bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 3
   myIL->MarkLabel( jumpTable[ 3 ] );
   myIL->Emit( OpCodes::Ldstr, "are three bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 4
   myIL->MarkLabel( jumpTable[ 4 ] );
   myIL->Emit( OpCodes::Ldstr, "are four bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Default case
   myIL->MarkLabel( defaultCase );
   myIL->Emit( OpCodes::Ldstr, "are many bananas" );
   myIL->MarkLabel( endOfMethod );
   myIL->Emit( OpCodes::Ret );
   return myTypeBuilder->CreateType();
}

int main()
{
   Type^ myType = BuildMyType();
   Console::Write( "Enter an integer between 0 and 5: " );
   int theValue = Convert::ToInt32( Console::ReadLine() );
   Console::WriteLine( "---" );
   Object^ myInstance = Activator::CreateInstance( myType, gcnew array<Object^>(0) );
   array<Object^>^temp1 = {theValue};
   Console::WriteLine( "Yes, there {0} today!", myType->InvokeMember( "SwitchMe", BindingFlags::InvokeMethod, nullptr, myInstance, temp1 ) );
}


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

class DynamicJumpTableDemo

{

   public static Type BuildMyType()
   {
	AppDomain myDomain = Thread.GetDomain();
	AssemblyName myAsmName = new AssemblyName();
	myAsmName.Name = "MyDynamicAssembly";

	AssemblyBuilder myAsmBuilder = myDomain.DefineDynamicAssembly(
						myAsmName,
						AssemblyBuilderAccess.Run);
	ModuleBuilder myModBuilder = myAsmBuilder.DefineDynamicModule(
						"MyJumpTableDemo");

	TypeBuilder myTypeBuilder = myModBuilder.DefineType("JumpTableDemo",
							TypeAttributes.Public);
	MethodBuilder myMthdBuilder = myTypeBuilder.DefineMethod("SwitchMe", 
				             MethodAttributes.Public |
				             MethodAttributes.Static,
                                             typeof(string), 
                                             new Type[] {typeof(int)});

	ILGenerator myIL = myMthdBuilder.GetILGenerator();

	Label defaultCase = myIL.DefineLabel();	
	Label endOfMethod = myIL.DefineLabel();	

	// We are initializing our jump table. Note that the labels
	// will be placed later using the MarkLabel method. 

	Label[] jumpTable = new Label[] { myIL.DefineLabel(),
					  myIL.DefineLabel(),
					  myIL.DefineLabel(),
					  myIL.DefineLabel(),
					  myIL.DefineLabel() };

	// arg0, the number we passed, is pushed onto the stack.
	// In this case, due to the design of the code sample,
	// the value pushed onto the stack happens to match the
	// index of the label (in IL terms, the index of the offset
	// in the jump table). If this is not the case, such as
	// when switching based on non-integer values, rules for the correspondence
	// between the possible case values and each index of the offsets
	// must be established outside of the ILGenerator.Emit calls,
	// much as a compiler would.

	myIL.Emit(OpCodes.Ldarg_0);
	myIL.Emit(OpCodes.Switch, jumpTable);
	
	// Branch on default case
	myIL.Emit(OpCodes.Br_S, defaultCase);

	// Case arg0 = 0
	myIL.MarkLabel(jumpTable[0]); 
	myIL.Emit(OpCodes.Ldstr, "are no bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 1
	myIL.MarkLabel(jumpTable[1]); 
	myIL.Emit(OpCodes.Ldstr, "is one banana");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 2
	myIL.MarkLabel(jumpTable[2]); 
	myIL.Emit(OpCodes.Ldstr, "are two bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 3
	myIL.MarkLabel(jumpTable[3]); 
	myIL.Emit(OpCodes.Ldstr, "are three bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 4
	myIL.MarkLabel(jumpTable[4]); 
	myIL.Emit(OpCodes.Ldstr, "are four bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Default case
	myIL.MarkLabel(defaultCase);
	myIL.Emit(OpCodes.Ldstr, "are many bananas");

	myIL.MarkLabel(endOfMethod);
	myIL.Emit(OpCodes.Ret);
	
	return myTypeBuilder.CreateType();

   }

   public static void Main()
   {
	Type myType = BuildMyType();
	
	Console.Write("Enter an integer between 0 and 5: ");
	int theValue = Convert.ToInt32(Console.ReadLine());

	Console.WriteLine("---");
	Object myInstance = Activator.CreateInstance(myType, new object[0]);	
	Console.WriteLine("Yes, there {0} today!", myType.InvokeMember("SwitchMe",
			  		           BindingFlags.InvokeMethod,
			  		           null,
			  		           myInstance,
			  		           new object[] {theValue}));  
			  
   }

}


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

 _

Class DynamicJumpTableDemo
   
   Public Shared Function BuildMyType() As Type

      Dim myDomain As AppDomain = Thread.GetDomain()
      Dim myAsmName As New AssemblyName()
      myAsmName.Name = "MyDynamicAssembly"
      
      Dim myAsmBuilder As AssemblyBuilder = myDomain.DefineDynamicAssembly(myAsmName, _
							AssemblyBuilderAccess.Run)
      Dim myModBuilder As ModuleBuilder = myAsmBuilder.DefineDynamicModule("MyJumpTableDemo")
      
      Dim myTypeBuilder As TypeBuilder = myModBuilder.DefineType("JumpTableDemo", _
								 TypeAttributes.Public)
      Dim myMthdBuilder As MethodBuilder = myTypeBuilder.DefineMethod("SwitchMe", _
						MethodAttributes.Public Or MethodAttributes.Static, _
						GetType(String), New Type() {GetType(Integer)})
      
      Dim myIL As ILGenerator = myMthdBuilder.GetILGenerator()
      
      Dim defaultCase As Label = myIL.DefineLabel()
      Dim endOfMethod As Label = myIL.DefineLabel()
      
      ' We are initializing our jump table. Note that the labels
      ' will be placed later using the MarkLabel method. 

      Dim jumpTable() As Label = {myIL.DefineLabel(), _
				  myIL.DefineLabel(), _
				  myIL.DefineLabel(), _
				  myIL.DefineLabel(), _
				  myIL.DefineLabel()}
      
      ' arg0, the number we passed, is pushed onto the stack.
      ' In this case, due to the design of the code sample,
      ' the value pushed onto the stack happens to match the
      ' index of the label (in IL terms, the index of the offset
      ' in the jump table). If this is not the case, such as
      ' when switching based on non-integer values, rules for the correspondence
      ' between the possible case values and each index of the offsets
      ' must be established outside of the ILGenerator.Emit calls,
      ' much as a compiler would.

      myIL.Emit(OpCodes.Ldarg_0)
      myIL.Emit(OpCodes.Switch, jumpTable)
      
      ' Branch on default case
      myIL.Emit(OpCodes.Br_S, defaultCase)
      
      ' Case arg0 = 0
      myIL.MarkLabel(jumpTable(0))
      myIL.Emit(OpCodes.Ldstr, "are no bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 1
      myIL.MarkLabel(jumpTable(1))
      myIL.Emit(OpCodes.Ldstr, "is one banana")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 2
      myIL.MarkLabel(jumpTable(2))
      myIL.Emit(OpCodes.Ldstr, "are two bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 3
      myIL.MarkLabel(jumpTable(3))
      myIL.Emit(OpCodes.Ldstr, "are three bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 4
      myIL.MarkLabel(jumpTable(4))
      myIL.Emit(OpCodes.Ldstr, "are four bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Default case
      myIL.MarkLabel(defaultCase)
      myIL.Emit(OpCodes.Ldstr, "are many bananas")
      
      myIL.MarkLabel(endOfMethod)
      myIL.Emit(OpCodes.Ret)
      
      Return myTypeBuilder.CreateType()

   End Function 'BuildMyType
    
   
   Public Shared Sub Main()

      Dim myType As Type = BuildMyType()
      
      Console.Write("Enter an integer between 0 and 5: ")
      Dim theValue As Integer = Convert.ToInt32(Console.ReadLine())
      
      Console.WriteLine("---")
      Dim myInstance As [Object] = Activator.CreateInstance(myType, New Object() {})
      Console.WriteLine("Yes, there {0} today!", myType.InvokeMember("SwitchMe", _
						 BindingFlags.InvokeMethod, Nothing, _
					         myInstance, New Object() {theValue}))

   End Sub 'Main

End Class 'DynamicJumpTableDemo

Remarks

Emits a switch table.

The instruction values are defined in the OpCodes enumeration.

Labels are created using DefineLabel and their location within the stream is fixed by using MarkLabel. If a single-byte instruction is used, the label can represent a jump of at most 127 bytes along the stream. opcode must represent a branch instruction. Because branches are relative instructions, label will be replaced with the correct offset to branch during the fixup process.

Emit(OpCode, MethodInfo) Emit(OpCode, MethodInfo) Emit(OpCode, MethodInfo)

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream followed by the metadata token for the given method.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, System::Reflection::MethodInfo ^ meth);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, System.Reflection.MethodInfo meth);
abstract member Emit : System.Reflection.Emit.OpCode * System.Reflection.MethodInfo -> unit
override this.Emit : System.Reflection.Emit.OpCode * System.Reflection.MethodInfo -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be emitted onto the stream.

meth
MethodInfo MethodInfo MethodInfo

A MethodInfo representing a method.

Exceptions

meth is a generic method for which the IsGenericMethodDefinition property is false.

Remarks

The instruction values are defined in the OpCodes enumeration.

The location of meth is recorded so that the instruction stream can be patched if necessary when persisting the module to a portable executable (PE) file.

If meth represents a generic method, it must be a generic method definition. That is, its MethodInfo.IsGenericMethodDefinition property must be true.

Emit(OpCode, ConstructorInfo) Emit(OpCode, ConstructorInfo) Emit(OpCode, ConstructorInfo)

Puts the specified instruction and metadata token for the specified constructor onto the Microsoft intermediate language (MSIL) stream of instructions.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, System::Reflection::ConstructorInfo ^ con);
[System.Runtime.InteropServices.ComVisible(true)]
public virtual void Emit (System.Reflection.Emit.OpCode opcode, System.Reflection.ConstructorInfo con);
abstract member Emit : System.Reflection.Emit.OpCode * System.Reflection.ConstructorInfo -> unit
override this.Emit : System.Reflection.Emit.OpCode * System.Reflection.ConstructorInfo -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be emitted onto the stream.

con
ConstructorInfo ConstructorInfo ConstructorInfo

A ConstructorInfo representing a constructor.

Exceptions

con is null. This exception is new in the .NET Framework 4.

Remarks

The instruction values are defined in the OpCodes enumeration.

The location of con is recorded so that the instruction stream can be patched if necessary when persisting the module to a portable executable (PE) file.

Emit(OpCode, Int64) Emit(OpCode, Int64) Emit(OpCode, Int64)

Puts the specified instruction and numerical argument onto the Microsoft intermediate language (MSIL) stream of instructions.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, long arg);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, long arg);
abstract member Emit : System.Reflection.Emit.OpCode * int64 -> unit
override this.Emit : System.Reflection.Emit.OpCode * int64 -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be put onto the stream.

arg
Int64 Int64 Int64

The numerical argument pushed onto the stream immediately after the instruction.

Remarks

The instruction values are defined in the OpCodes enumeration.

Emit(OpCode, Int32) Emit(OpCode, Int32) Emit(OpCode, Int32)

Puts the specified instruction and numerical argument onto the Microsoft intermediate language (MSIL) stream of instructions.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, int arg);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, int arg);
abstract member Emit : System.Reflection.Emit.OpCode * int -> unit
override this.Emit : System.Reflection.Emit.OpCode * int -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be put onto the stream.

arg
Int32 Int32 Int32

The numerical argument pushed onto the stream immediately after the instruction.

Remarks

The instruction values are defined in the OpCodes enumeration.

Emit(OpCode, Int16) Emit(OpCode, Int16) Emit(OpCode, Int16)

Puts the specified instruction and numerical argument onto the Microsoft intermediate language (MSIL) stream of instructions.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, short arg);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, short arg);
abstract member Emit : System.Reflection.Emit.OpCode * int16 -> unit
override this.Emit : System.Reflection.Emit.OpCode * int16 -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be emitted onto the stream.

arg
Int16 Int16 Int16

The Int argument pushed onto the stream immediately after the instruction.

Remarks

The instruction values are defined in the OpCodes enumeration.

Emit(OpCode, Double) Emit(OpCode, Double) Emit(OpCode, Double)

Puts the specified instruction and numerical argument onto the Microsoft intermediate language (MSIL) stream of instructions.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, double arg);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, double arg);
abstract member Emit : System.Reflection.Emit.OpCode * double -> unit
override this.Emit : System.Reflection.Emit.OpCode * double -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be put onto the stream. Defined in the OpCodes enumeration.

arg
Double Double Double

The numerical argument pushed onto the stream immediately after the instruction.

Remarks

The instruction values are defined in the OpCodes enumeration.

Emit(OpCode, Byte) Emit(OpCode, Byte) Emit(OpCode, Byte)

Puts the specified instruction and character argument onto the Microsoft intermediate language (MSIL) stream of instructions.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, System::Byte arg);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, byte arg);
abstract member Emit : System.Reflection.Emit.OpCode * byte -> unit
override this.Emit : System.Reflection.Emit.OpCode * byte -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be put onto the stream.

arg
Byte Byte Byte

The character argument pushed onto the stream immediately after the instruction.

Remarks

The instruction values are defined in the OpCodes enumeration.

Emit(OpCode) Emit(OpCode) Emit(OpCode)

Puts the specified instruction onto the stream of instructions.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode);
public virtual void Emit (System.Reflection.Emit.OpCode opcode);
abstract member Emit : System.Reflection.Emit.OpCode -> unit
override this.Emit : System.Reflection.Emit.OpCode -> unit
Parameters
opcode
OpCode OpCode OpCode

The Microsoft Intermediate Language (MSIL) instruction to be put onto the stream.

Examples

The code sample below demonstrates the use of Emit to generate MSIL output via an instance of ILGenerator.

using namespace System;
using namespace System::Threading;
using namespace System::Reflection;
using namespace System::Reflection::Emit;
Type^ BuildMyType()
{
   AppDomain^ myDomain = Thread::GetDomain();
   AssemblyName^ myAsmName = gcnew AssemblyName;
   myAsmName->Name = "MyDynamicAssembly";
   AssemblyBuilder^ myAsmBuilder = myDomain->DefineDynamicAssembly( myAsmName, AssemblyBuilderAccess::Run );
   ModuleBuilder^ myModBuilder = myAsmBuilder->DefineDynamicModule( "MyJumpTableDemo" );
   TypeBuilder^ myTypeBuilder = myModBuilder->DefineType( "JumpTableDemo", TypeAttributes::Public );
   array<Type^>^temp0 = {int::typeid};
   MethodBuilder^ myMthdBuilder = myTypeBuilder->DefineMethod( "SwitchMe", static_cast<MethodAttributes>(MethodAttributes::Public | MethodAttributes::Static), String::typeid, temp0 );
   ILGenerator^ myIL = myMthdBuilder->GetILGenerator();
   Label defaultCase = myIL->DefineLabel();
   Label endOfMethod = myIL->DefineLabel();
   
   // We are initializing our jump table. Note that the labels
   // will be placed later using the MarkLabel method.
   array<Label>^jumpTable = gcnew array<Label>(5);
   jumpTable[ 0 ] = myIL->DefineLabel();
   jumpTable[ 1 ] = myIL->DefineLabel();
   jumpTable[ 2 ] = myIL->DefineLabel();
   jumpTable[ 3 ] = myIL->DefineLabel();
   jumpTable[ 4 ] = myIL->DefineLabel();
   
   // arg0, the number we passed, is pushed onto the stack.
   // In this case, due to the design of the code sample,
   // the value pushed onto the stack happens to match the
   // index of the label (in IL terms, the index of the offset
   // in the jump table). If this is not the case, such as
   // when switching based on non-integer values, rules for the correspondence
   // between the possible case values and each index of the offsets
   // must be established outside of the ILGenerator::Emit calls,
   // much as a compiler would.
   myIL->Emit( OpCodes::Ldarg_0 );
   myIL->Emit( OpCodes::Switch, jumpTable );
   
   // Branch on default case
   myIL->Emit( OpCodes::Br_S, defaultCase );
   
   // Case arg0 = 0
   myIL->MarkLabel( jumpTable[ 0 ] );
   myIL->Emit( OpCodes::Ldstr, "are no bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 1
   myIL->MarkLabel( jumpTable[ 1 ] );
   myIL->Emit( OpCodes::Ldstr, "is one banana" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 2
   myIL->MarkLabel( jumpTable[ 2 ] );
   myIL->Emit( OpCodes::Ldstr, "are two bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 3
   myIL->MarkLabel( jumpTable[ 3 ] );
   myIL->Emit( OpCodes::Ldstr, "are three bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 4
   myIL->MarkLabel( jumpTable[ 4 ] );
   myIL->Emit( OpCodes::Ldstr, "are four bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Default case
   myIL->MarkLabel( defaultCase );
   myIL->Emit( OpCodes::Ldstr, "are many bananas" );
   myIL->MarkLabel( endOfMethod );
   myIL->Emit( OpCodes::Ret );
   return myTypeBuilder->CreateType();
}

int main()
{
   Type^ myType = BuildMyType();
   Console::Write( "Enter an integer between 0 and 5: " );
   int theValue = Convert::ToInt32( Console::ReadLine() );
   Console::WriteLine( "---" );
   Object^ myInstance = Activator::CreateInstance( myType, gcnew array<Object^>(0) );
   array<Object^>^temp1 = {theValue};
   Console::WriteLine( "Yes, there {0} today!", myType->InvokeMember( "SwitchMe", BindingFlags::InvokeMethod, nullptr, myInstance, temp1 ) );
}


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

class DynamicJumpTableDemo

{

   public static Type BuildMyType()
   {
	AppDomain myDomain = Thread.GetDomain();
	AssemblyName myAsmName = new AssemblyName();
	myAsmName.Name = "MyDynamicAssembly";

	AssemblyBuilder myAsmBuilder = myDomain.DefineDynamicAssembly(
						myAsmName,
						AssemblyBuilderAccess.Run);
	ModuleBuilder myModBuilder = myAsmBuilder.DefineDynamicModule(
						"MyJumpTableDemo");

	TypeBuilder myTypeBuilder = myModBuilder.DefineType("JumpTableDemo",
							TypeAttributes.Public);
	MethodBuilder myMthdBuilder = myTypeBuilder.DefineMethod("SwitchMe", 
				             MethodAttributes.Public |
				             MethodAttributes.Static,
                                             typeof(string), 
                                             new Type[] {typeof(int)});

	ILGenerator myIL = myMthdBuilder.GetILGenerator();

	Label defaultCase = myIL.DefineLabel();	
	Label endOfMethod = myIL.DefineLabel();	

	// We are initializing our jump table. Note that the labels
	// will be placed later using the MarkLabel method. 

	Label[] jumpTable = new Label[] { myIL.DefineLabel(),
					  myIL.DefineLabel(),
					  myIL.DefineLabel(),
					  myIL.DefineLabel(),
					  myIL.DefineLabel() };

	// arg0, the number we passed, is pushed onto the stack.
	// In this case, due to the design of the code sample,
	// the value pushed onto the stack happens to match the
	// index of the label (in IL terms, the index of the offset
	// in the jump table). If this is not the case, such as
	// when switching based on non-integer values, rules for the correspondence
	// between the possible case values and each index of the offsets
	// must be established outside of the ILGenerator.Emit calls,
	// much as a compiler would.

	myIL.Emit(OpCodes.Ldarg_0);
	myIL.Emit(OpCodes.Switch, jumpTable);
	
	// Branch on default case
	myIL.Emit(OpCodes.Br_S, defaultCase);

	// Case arg0 = 0
	myIL.MarkLabel(jumpTable[0]); 
	myIL.Emit(OpCodes.Ldstr, "are no bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 1
	myIL.MarkLabel(jumpTable[1]); 
	myIL.Emit(OpCodes.Ldstr, "is one banana");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 2
	myIL.MarkLabel(jumpTable[2]); 
	myIL.Emit(OpCodes.Ldstr, "are two bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 3
	myIL.MarkLabel(jumpTable[3]); 
	myIL.Emit(OpCodes.Ldstr, "are three bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 4
	myIL.MarkLabel(jumpTable[4]); 
	myIL.Emit(OpCodes.Ldstr, "are four bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Default case
	myIL.MarkLabel(defaultCase);
	myIL.Emit(OpCodes.Ldstr, "are many bananas");

	myIL.MarkLabel(endOfMethod);
	myIL.Emit(OpCodes.Ret);
	
	return myTypeBuilder.CreateType();

   }

   public static void Main()
   {
	Type myType = BuildMyType();
	
	Console.Write("Enter an integer between 0 and 5: ");
	int theValue = Convert.ToInt32(Console.ReadLine());

	Console.WriteLine("---");
	Object myInstance = Activator.CreateInstance(myType, new object[0]);	
	Console.WriteLine("Yes, there {0} today!", myType.InvokeMember("SwitchMe",
			  		           BindingFlags.InvokeMethod,
			  		           null,
			  		           myInstance,
			  		           new object[] {theValue}));  
			  
   }

}


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

 _

Class DynamicJumpTableDemo
   
   Public Shared Function BuildMyType() As Type

      Dim myDomain As AppDomain = Thread.GetDomain()
      Dim myAsmName As New AssemblyName()
      myAsmName.Name = "MyDynamicAssembly"
      
      Dim myAsmBuilder As AssemblyBuilder = myDomain.DefineDynamicAssembly(myAsmName, _
							AssemblyBuilderAccess.Run)
      Dim myModBuilder As ModuleBuilder = myAsmBuilder.DefineDynamicModule("MyJumpTableDemo")
      
      Dim myTypeBuilder As TypeBuilder = myModBuilder.DefineType("JumpTableDemo", _
								 TypeAttributes.Public)
      Dim myMthdBuilder As MethodBuilder = myTypeBuilder.DefineMethod("SwitchMe", _
						MethodAttributes.Public Or MethodAttributes.Static, _
						GetType(String), New Type() {GetType(Integer)})
      
      Dim myIL As ILGenerator = myMthdBuilder.GetILGenerator()
      
      Dim defaultCase As Label = myIL.DefineLabel()
      Dim endOfMethod As Label = myIL.DefineLabel()
      
      ' We are initializing our jump table. Note that the labels
      ' will be placed later using the MarkLabel method. 

      Dim jumpTable() As Label = {myIL.DefineLabel(), _
				  myIL.DefineLabel(), _
				  myIL.DefineLabel(), _
				  myIL.DefineLabel(), _
				  myIL.DefineLabel()}
      
      ' arg0, the number we passed, is pushed onto the stack.
      ' In this case, due to the design of the code sample,
      ' the value pushed onto the stack happens to match the
      ' index of the label (in IL terms, the index of the offset
      ' in the jump table). If this is not the case, such as
      ' when switching based on non-integer values, rules for the correspondence
      ' between the possible case values and each index of the offsets
      ' must be established outside of the ILGenerator.Emit calls,
      ' much as a compiler would.

      myIL.Emit(OpCodes.Ldarg_0)
      myIL.Emit(OpCodes.Switch, jumpTable)
      
      ' Branch on default case
      myIL.Emit(OpCodes.Br_S, defaultCase)
      
      ' Case arg0 = 0
      myIL.MarkLabel(jumpTable(0))
      myIL.Emit(OpCodes.Ldstr, "are no bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 1
      myIL.MarkLabel(jumpTable(1))
      myIL.Emit(OpCodes.Ldstr, "is one banana")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 2
      myIL.MarkLabel(jumpTable(2))
      myIL.Emit(OpCodes.Ldstr, "are two bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 3
      myIL.MarkLabel(jumpTable(3))
      myIL.Emit(OpCodes.Ldstr, "are three bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 4
      myIL.MarkLabel(jumpTable(4))
      myIL.Emit(OpCodes.Ldstr, "are four bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Default case
      myIL.MarkLabel(defaultCase)
      myIL.Emit(OpCodes.Ldstr, "are many bananas")
      
      myIL.MarkLabel(endOfMethod)
      myIL.Emit(OpCodes.Ret)
      
      Return myTypeBuilder.CreateType()

   End Function 'BuildMyType
    
   
   Public Shared Sub Main()

      Dim myType As Type = BuildMyType()
      
      Console.Write("Enter an integer between 0 and 5: ")
      Dim theValue As Integer = Convert.ToInt32(Console.ReadLine())
      
      Console.WriteLine("---")
      Dim myInstance As [Object] = Activator.CreateInstance(myType, New Object() {})
      Console.WriteLine("Yes, there {0} today!", myType.InvokeMember("SwitchMe", _
						 BindingFlags.InvokeMethod, Nothing, _
					         myInstance, New Object() {theValue}))

   End Sub 'Main

End Class 'DynamicJumpTableDemo

Remarks

If the opcode parameter requires an argument, the caller must ensure that the argument length matches the length of the declared parameter. Otherwise, results will be unpredictable. For example, if the Emit instruction requires a 2-byte operand and the caller supplies a 4-byte operand, the runtime will emit two additional bytes to the instruction stream. These extra bytes will be Nop instructions.

The instruction values are defined in OpCodes.

Emit(OpCode, Label) Emit(OpCode, Label) Emit(OpCode, Label)

Puts the specified instruction onto the Microsoft intermediate language (MSIL) stream and leaves space to include a label when fixes are done.

public:
 virtual void Emit(System::Reflection::Emit::OpCode opcode, System::Reflection::Emit::Label label);
public virtual void Emit (System.Reflection.Emit.OpCode opcode, System.Reflection.Emit.Label label);
abstract member Emit : System.Reflection.Emit.OpCode * System.Reflection.Emit.Label -> unit
override this.Emit : System.Reflection.Emit.OpCode * System.Reflection.Emit.Label -> unit
Parameters
opcode
OpCode OpCode OpCode

The MSIL instruction to be emitted onto the stream.

label
Label Label Label

The label to which to branch from this location.

Examples

The code sample below illustrates the creation of a dynamic method with a jump table. The jump table is built using an array of Label.

using namespace System;
using namespace System::Threading;
using namespace System::Reflection;
using namespace System::Reflection::Emit;
Type^ BuildMyType()
{
   AppDomain^ myDomain = Thread::GetDomain();
   AssemblyName^ myAsmName = gcnew AssemblyName;
   myAsmName->Name = "MyDynamicAssembly";
   AssemblyBuilder^ myAsmBuilder = myDomain->DefineDynamicAssembly( myAsmName, AssemblyBuilderAccess::Run );
   ModuleBuilder^ myModBuilder = myAsmBuilder->DefineDynamicModule( "MyJumpTableDemo" );
   TypeBuilder^ myTypeBuilder = myModBuilder->DefineType( "JumpTableDemo", TypeAttributes::Public );
   array<Type^>^temp0 = {int::typeid};
   MethodBuilder^ myMthdBuilder = myTypeBuilder->DefineMethod( "SwitchMe", static_cast<MethodAttributes>(MethodAttributes::Public | MethodAttributes::Static), String::typeid, temp0 );
   ILGenerator^ myIL = myMthdBuilder->GetILGenerator();
   Label defaultCase = myIL->DefineLabel();
   Label endOfMethod = myIL->DefineLabel();
   
   // We are initializing our jump table. Note that the labels
   // will be placed later using the MarkLabel method.
   array<Label>^jumpTable = gcnew array<Label>(5);
   jumpTable[ 0 ] = myIL->DefineLabel();
   jumpTable[ 1 ] = myIL->DefineLabel();
   jumpTable[ 2 ] = myIL->DefineLabel();
   jumpTable[ 3 ] = myIL->DefineLabel();
   jumpTable[ 4 ] = myIL->DefineLabel();
   
   // arg0, the number we passed, is pushed onto the stack.
   // In this case, due to the design of the code sample,
   // the value pushed onto the stack happens to match the
   // index of the label (in IL terms, the index of the offset
   // in the jump table). If this is not the case, such as
   // when switching based on non-integer values, rules for the correspondence
   // between the possible case values and each index of the offsets
   // must be established outside of the ILGenerator::Emit calls,
   // much as a compiler would.
   myIL->Emit( OpCodes::Ldarg_0 );
   myIL->Emit( OpCodes::Switch, jumpTable );
   
   // Branch on default case
   myIL->Emit( OpCodes::Br_S, defaultCase );
   
   // Case arg0 = 0
   myIL->MarkLabel( jumpTable[ 0 ] );
   myIL->Emit( OpCodes::Ldstr, "are no bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 1
   myIL->MarkLabel( jumpTable[ 1 ] );
   myIL->Emit( OpCodes::Ldstr, "is one banana" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 2
   myIL->MarkLabel( jumpTable[ 2 ] );
   myIL->Emit( OpCodes::Ldstr, "are two bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 3
   myIL->MarkLabel( jumpTable[ 3 ] );
   myIL->Emit( OpCodes::Ldstr, "are three bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Case arg0 = 4
   myIL->MarkLabel( jumpTable[ 4 ] );
   myIL->Emit( OpCodes::Ldstr, "are four bananas" );
   myIL->Emit( OpCodes::Br_S, endOfMethod );
   
   // Default case
   myIL->MarkLabel( defaultCase );
   myIL->Emit( OpCodes::Ldstr, "are many bananas" );
   myIL->MarkLabel( endOfMethod );
   myIL->Emit( OpCodes::Ret );
   return myTypeBuilder->CreateType();
}

int main()
{
   Type^ myType = BuildMyType();
   Console::Write( "Enter an integer between 0 and 5: " );
   int theValue = Convert::ToInt32( Console::ReadLine() );
   Console::WriteLine( "---" );
   Object^ myInstance = Activator::CreateInstance( myType, gcnew array<Object^>(0) );
   array<Object^>^temp1 = {theValue};
   Console::WriteLine( "Yes, there {0} today!", myType->InvokeMember( "SwitchMe", BindingFlags::InvokeMethod, nullptr, myInstance, temp1 ) );
}


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

class DynamicJumpTableDemo

{

   public static Type BuildMyType()
   {
	AppDomain myDomain = Thread.GetDomain();
	AssemblyName myAsmName = new AssemblyName();
	myAsmName.Name = "MyDynamicAssembly";

	AssemblyBuilder myAsmBuilder = myDomain.DefineDynamicAssembly(
						myAsmName,
						AssemblyBuilderAccess.Run);
	ModuleBuilder myModBuilder = myAsmBuilder.DefineDynamicModule(
						"MyJumpTableDemo");

	TypeBuilder myTypeBuilder = myModBuilder.DefineType("JumpTableDemo",
							TypeAttributes.Public);
	MethodBuilder myMthdBuilder = myTypeBuilder.DefineMethod("SwitchMe", 
				             MethodAttributes.Public |
				             MethodAttributes.Static,
                                             typeof(string), 
                                             new Type[] {typeof(int)});

	ILGenerator myIL = myMthdBuilder.GetILGenerator();

	Label defaultCase = myIL.DefineLabel();	
	Label endOfMethod = myIL.DefineLabel();	

	// We are initializing our jump table. Note that the labels
	// will be placed later using the MarkLabel method. 

	Label[] jumpTable = new Label[] { myIL.DefineLabel(),
					  myIL.DefineLabel(),
					  myIL.DefineLabel(),
					  myIL.DefineLabel(),
					  myIL.DefineLabel() };

	// arg0, the number we passed, is pushed onto the stack.
	// In this case, due to the design of the code sample,
	// the value pushed onto the stack happens to match the
	// index of the label (in IL terms, the index of the offset
	// in the jump table). If this is not the case, such as
	// when switching based on non-integer values, rules for the correspondence
	// between the possible case values and each index of the offsets
	// must be established outside of the ILGenerator.Emit calls,
	// much as a compiler would.

	myIL.Emit(OpCodes.Ldarg_0);
	myIL.Emit(OpCodes.Switch, jumpTable);
	
	// Branch on default case
	myIL.Emit(OpCodes.Br_S, defaultCase);

	// Case arg0 = 0
	myIL.MarkLabel(jumpTable[0]); 
	myIL.Emit(OpCodes.Ldstr, "are no bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 1
	myIL.MarkLabel(jumpTable[1]); 
	myIL.Emit(OpCodes.Ldstr, "is one banana");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 2
	myIL.MarkLabel(jumpTable[2]); 
	myIL.Emit(OpCodes.Ldstr, "are two bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 3
	myIL.MarkLabel(jumpTable[3]); 
	myIL.Emit(OpCodes.Ldstr, "are three bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Case arg0 = 4
	myIL.MarkLabel(jumpTable[4]); 
	myIL.Emit(OpCodes.Ldstr, "are four bananas");
	myIL.Emit(OpCodes.Br_S, endOfMethod);

	// Default case
	myIL.MarkLabel(defaultCase);
	myIL.Emit(OpCodes.Ldstr, "are many bananas");

	myIL.MarkLabel(endOfMethod);
	myIL.Emit(OpCodes.Ret);
	
	return myTypeBuilder.CreateType();

   }

   public static void Main()
   {
	Type myType = BuildMyType();
	
	Console.Write("Enter an integer between 0 and 5: ");
	int theValue = Convert.ToInt32(Console.ReadLine());

	Console.WriteLine("---");
	Object myInstance = Activator.CreateInstance(myType, new object[0]);	
	Console.WriteLine("Yes, there {0} today!", myType.InvokeMember("SwitchMe",
			  		           BindingFlags.InvokeMethod,
			  		           null,
			  		           myInstance,
			  		           new object[] {theValue}));  
			  
   }

}


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

 _

Class DynamicJumpTableDemo
   
   Public Shared Function BuildMyType() As Type

      Dim myDomain As AppDomain = Thread.GetDomain()
      Dim myAsmName As New AssemblyName()
      myAsmName.Name = "MyDynamicAssembly"
      
      Dim myAsmBuilder As AssemblyBuilder = myDomain.DefineDynamicAssembly(myAsmName, _
							AssemblyBuilderAccess.Run)
      Dim myModBuilder As ModuleBuilder = myAsmBuilder.DefineDynamicModule("MyJumpTableDemo")
      
      Dim myTypeBuilder As TypeBuilder = myModBuilder.DefineType("JumpTableDemo", _
								 TypeAttributes.Public)
      Dim myMthdBuilder As MethodBuilder = myTypeBuilder.DefineMethod("SwitchMe", _
						MethodAttributes.Public Or MethodAttributes.Static, _
						GetType(String), New Type() {GetType(Integer)})
      
      Dim myIL As ILGenerator = myMthdBuilder.GetILGenerator()
      
      Dim defaultCase As Label = myIL.DefineLabel()
      Dim endOfMethod As Label = myIL.DefineLabel()
      
      ' We are initializing our jump table. Note that the labels
      ' will be placed later using the MarkLabel method. 

      Dim jumpTable() As Label = {myIL.DefineLabel(), _
				  myIL.DefineLabel(), _
				  myIL.DefineLabel(), _
				  myIL.DefineLabel(), _
				  myIL.DefineLabel()}
      
      ' arg0, the number we passed, is pushed onto the stack.
      ' In this case, due to the design of the code sample,
      ' the value pushed onto the stack happens to match the
      ' index of the label (in IL terms, the index of the offset
      ' in the jump table). If this is not the case, such as
      ' when switching based on non-integer values, rules for the correspondence
      ' between the possible case values and each index of the offsets
      ' must be established outside of the ILGenerator.Emit calls,
      ' much as a compiler would.

      myIL.Emit(OpCodes.Ldarg_0)
      myIL.Emit(OpCodes.Switch, jumpTable)
      
      ' Branch on default case
      myIL.Emit(OpCodes.Br_S, defaultCase)
      
      ' Case arg0 = 0
      myIL.MarkLabel(jumpTable(0))
      myIL.Emit(OpCodes.Ldstr, "are no bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 1
      myIL.MarkLabel(jumpTable(1))
      myIL.Emit(OpCodes.Ldstr, "is one banana")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 2
      myIL.MarkLabel(jumpTable(2))
      myIL.Emit(OpCodes.Ldstr, "are two bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 3
      myIL.MarkLabel(jumpTable(3))
      myIL.Emit(OpCodes.Ldstr, "are three bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Case arg0 = 4
      myIL.MarkLabel(jumpTable(4))
      myIL.Emit(OpCodes.Ldstr, "are four bananas")
      myIL.Emit(OpCodes.Br_S, endOfMethod)
      
      ' Default case
      myIL.MarkLabel(defaultCase)
      myIL.Emit(OpCodes.Ldstr, "are many bananas")
      
      myIL.MarkLabel(endOfMethod)
      myIL.Emit(OpCodes.Ret)
      
      Return myTypeBuilder.CreateType()

   End Function 'BuildMyType
    
   
   Public Shared Sub Main()

      Dim myType As Type = BuildMyType()
      
      Console.Write("Enter an integer between 0 and 5: ")
      Dim theValue As Integer = Convert.ToInt32(Console.ReadLine())
      
      Console.WriteLine("---")
      Dim myInstance As [Object] = Activator.CreateInstance(myType, New Object() {})
      Console.WriteLine("Yes, there {0} today!", myType.InvokeMember("SwitchMe", _
						 BindingFlags.InvokeMethod, Nothing, _
					         myInstance, New Object() {theValue}))

   End Sub 'Main

End Class 'DynamicJumpTableDemo

Remarks

The instruction values are defined in the OpCodes enumeration.

Labels are created using DefineLabel, and their location within the stream is fixed by using MarkLabel. If a single-byte instruction is used, the label can represent a jump of at most 127 bytes along the stream. opcode must represent a branch instruction. Because branches are relative instructions, label will be replaced with the correct offset to branch during the fixup process.

Applies to