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Deklariert eine neue Sprungmarke.
Namespace: System.Reflection.Emit
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Overridable Function DefineLabel As Label
'Usage
Dim instance As ILGenerator
Dim returnValue As Label
returnValue = instance.DefineLabel
public virtual Label DefineLabel ()
public:
virtual Label DefineLabel ()
public Label DefineLabel ()
public function DefineLabel () : Label
Rückgabewert
Gibt eine neue Sprungmarke zurück, die als Token für Verzweigungen verwendet werden kann.
Hinweise
Um die Position der Sprungmarke innerhalb des Streams festzulegen, müssen Sie MarkLabel aufrufen.
Dies ist lediglich ein Token, das noch keine bestimmte Position innerhalb des Streams darstellt.
Beispiel
Das folgende Codebeispiel veranschaulicht die kontextabhängige Verwendung der DefineLabel-Methode.
Imports System
Imports System.Threading
Imports System.Reflection
Imports System.Reflection.Emit
_
Class ILLabelDemo
Public Shared Function BuildAdderType() As Type
Dim myDomain As AppDomain = Thread.GetDomain()
Dim myAsmName As New AssemblyName()
myAsmName.Name = "AdderExceptionAsm"
Dim myAsmBldr As AssemblyBuilder = myDomain.DefineDynamicAssembly(myAsmName, _
AssemblyBuilderAccess.Run)
Dim myModBldr As ModuleBuilder = myAsmBldr.DefineDynamicModule("AdderExceptionMod")
Dim myTypeBldr As TypeBuilder = myModBldr.DefineType("Adder")
Dim adderParams() As Type = {GetType(Integer), GetType(Integer)}
' This method will add two numbers which are 100 or less. If either of the
' passed integer vales are greater than 100, it will return the value of -1.
Dim adderBldr As MethodBuilder = myTypeBldr.DefineMethod("DoAdd", _
MethodAttributes.Public Or MethodAttributes.Static, _
GetType(Integer), adderParams)
Dim adderIL As ILGenerator = adderBldr.GetILGenerator()
' In order to successfully branch, we need to create labels
' representing the offset IL instruction block to branch to.
' These labels, when the MarkLabel(Label) method is invoked,
' will specify the IL instruction to branch to.
Dim failed As Label = adderIL.DefineLabel()
Dim endOfMthd As Label = adderIL.DefineLabel()
' First, load argument 0 and the integer value of "100" onto the
' stack. If arg0 > 100, branch to the label "failed", which is marked
' as the address of the block that loads -1 onto the stack, bypassing
' the addition.
adderIL.Emit(OpCodes.Ldarg_0)
adderIL.Emit(OpCodes.Ldc_I4_S, 100)
adderIL.Emit(OpCodes.Bgt_S, failed)
' Now, check to see if argument 1 was greater than 100. If it was,
' branch to "failed." Otherwise, fall through and perform the addition,
' branching unconditionally to the instruction at the label "endOfMthd".
adderIL.Emit(OpCodes.Ldarg_1)
adderIL.Emit(OpCodes.Ldc_I4_S, 100)
adderIL.Emit(OpCodes.Bgt_S, failed)
adderIL.Emit(OpCodes.Ldarg_0)
adderIL.Emit(OpCodes.Ldarg_1)
adderIL.Emit(OpCodes.Add_Ovf_Un)
adderIL.Emit(OpCodes.Br_S, endOfMthd)
' If this label is branched to (the failure case), load -1 onto the stack
' and fall through to the return opcode.
adderIL.MarkLabel(failed)
adderIL.Emit(OpCodes.Ldc_I4_M1)
' The end of the method. If both values were less than 100, the
' correct result will return. If one of the arguments was greater
' than 100, the result will be -1.
adderIL.MarkLabel(endOfMthd)
adderIL.Emit(OpCodes.Ret)
Return myTypeBldr.CreateType()
End Function 'BuildAdderType
Public Shared Sub Main()
Dim adderType As Type = BuildAdderType()
Dim addIns As Object = Activator.CreateInstance(adderType)
Dim addParams(1) As Object
Console.Write("Enter an integer value: ")
addParams(0) = CType(Convert.ToInt32(Console.ReadLine()), Object)
Console.Write("Enter another integer value: ")
addParams(1) = CType(Convert.ToInt32(Console.ReadLine()), Object)
Console.WriteLine("---")
Dim adderResult As Integer = CInt(adderType.InvokeMember("DoAdd", _
BindingFlags.InvokeMethod, Nothing, _
addIns, addParams))
If adderResult <> - 1 Then
Console.WriteLine("{0} + {1} = {2}", addParams(0), addParams(1), adderResult)
Else
Console.WriteLine("One of the integers to add was greater than 100!")
End If
End Sub 'Main
End Class 'ILLabelDemo
using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;
class ILLabelDemo {
public static Type BuildAdderType() {
AppDomain myDomain = Thread.GetDomain();
AssemblyName myAsmName = new AssemblyName();
myAsmName.Name = "AdderExceptionAsm";
AssemblyBuilder myAsmBldr = myDomain.DefineDynamicAssembly(myAsmName,
AssemblyBuilderAccess.Run);
ModuleBuilder myModBldr = myAsmBldr.DefineDynamicModule("AdderExceptionMod");
TypeBuilder myTypeBldr = myModBldr.DefineType("Adder");
Type[] adderParams = new Type[] {typeof(int), typeof(int)};
// This method will add two numbers which are 100 or less. If either of the
// passed integer vales are greater than 100, it will return the value of -1.
MethodBuilder adderBldr = myTypeBldr.DefineMethod("DoAdd",
MethodAttributes.Public |
MethodAttributes.Static,
typeof(int),
adderParams);
ILGenerator adderIL = adderBldr.GetILGenerator();
// In order to successfully branch, we need to create labels
// representing the offset IL instruction block to branch to.
// These labels, when the MarkLabel(Label) method is invoked,
// will specify the IL instruction to branch to.
Label failed = adderIL.DefineLabel();
Label endOfMthd = adderIL.DefineLabel();
// First, load argument 0 and the integer value of "100" onto the
// stack. If arg0 > 100, branch to the label "failed", which is marked
// as the address of the block that loads -1 onto the stack, bypassing
// the addition.
adderIL.Emit(OpCodes.Ldarg_0);
adderIL.Emit(OpCodes.Ldc_I4_S, 100);
adderIL.Emit(OpCodes.Bgt_S, failed);
// Now, check to see if argument 1 was greater than 100. If it was,
// branch to "failed." Otherwise, fall through and perform the addition,
// branching unconditionally to the instruction at the label "endOfMthd".
adderIL.Emit(OpCodes.Ldarg_1);
adderIL.Emit(OpCodes.Ldc_I4_S, 100);
adderIL.Emit(OpCodes.Bgt_S, failed);
adderIL.Emit(OpCodes.Ldarg_0);
adderIL.Emit(OpCodes.Ldarg_1);
adderIL.Emit(OpCodes.Add_Ovf_Un);
adderIL.Emit(OpCodes.Br_S, endOfMthd);
// If this label is branched to (the failure case), load -1 onto the stack
// and fall through to the return opcode.
adderIL.MarkLabel(failed);
adderIL.Emit(OpCodes.Ldc_I4_M1);
// The end of the method. If both values were less than 100, the
// correct result will return. If one of the arguments was greater
// than 100, the result will be -1.
adderIL.MarkLabel(endOfMthd);
adderIL.Emit(OpCodes.Ret);
return myTypeBldr.CreateType();
}
public static void Main() {
Type adderType = BuildAdderType();
object addIns = Activator.CreateInstance(adderType);
object[] addParams = new object[2];
Console.Write("Enter an integer value: ");
addParams[0] = (object)Convert.ToInt32(Console.ReadLine());
Console.Write("Enter another integer value: ");
addParams[1] = (object)Convert.ToInt32(Console.ReadLine());
Console.WriteLine("---");
int adderResult = (int)adderType.InvokeMember("DoAdd",
BindingFlags.InvokeMethod,
null,
addIns,
addParams);
if (adderResult != -1) {
Console.WriteLine("{0} + {1} = {2}", addParams[0], addParams[1],
adderResult);
} else {
Console.WriteLine("One of the integers to add was greater than 100!");
}
}
}
using namespace System;
using namespace System::Threading;
using namespace System::Reflection;
using namespace System::Reflection::Emit;
Type^ BuildAdderType()
{
AppDomain^ myDomain = Thread::GetDomain();
AssemblyName^ myAsmName = gcnew AssemblyName;
myAsmName->Name = "AdderExceptionAsm";
AssemblyBuilder^ myAsmBldr = myDomain->DefineDynamicAssembly( myAsmName, AssemblyBuilderAccess::Run );
ModuleBuilder^ myModBldr = myAsmBldr->DefineDynamicModule( "AdderExceptionMod" );
TypeBuilder^ myTypeBldr = myModBldr->DefineType( "Adder" );
array<Type^>^adderParams = {int::typeid,int::typeid};
// This method will add two numbers which are 100 or less. If either of the
// passed integer vales are greater than 100, it will return the value of -1.
MethodBuilder^ adderBldr = myTypeBldr->DefineMethod( "DoAdd", static_cast<MethodAttributes>(MethodAttributes::Public | MethodAttributes::Static), int::typeid, adderParams );
ILGenerator^ adderIL = adderBldr->GetILGenerator();
// In order to successfully branch, we need to create labels
// representing the offset IL instruction block to branch to.
// These labels, when the MarkLabel(Label) method is invoked,
// will specify the IL instruction to branch to.
Label failed = adderIL->DefineLabel();
Label endOfMthd = adderIL->DefineLabel();
// First, load argument 0 and the integer value of "100" onto the
// stack. If arg0 > 100, branch to the label "failed", which is marked
// as the address of the block that loads -1 onto the stack, bypassing
// the addition.
adderIL->Emit( OpCodes::Ldarg_0 );
adderIL->Emit( OpCodes::Ldc_I4_S, 100 );
adderIL->Emit( OpCodes::Bgt_S, failed );
// Now, check to see if argument 1 was greater than 100. If it was,
// branch to "failed." Otherwise, fall through and perform the addition,
// branching unconditionally to the instruction at the label "endOfMthd".
adderIL->Emit( OpCodes::Ldarg_1 );
adderIL->Emit( OpCodes::Ldc_I4_S, 100 );
adderIL->Emit( OpCodes::Bgt_S, failed );
adderIL->Emit( OpCodes::Ldarg_0 );
adderIL->Emit( OpCodes::Ldarg_1 );
adderIL->Emit( OpCodes::Add_Ovf_Un );
adderIL->Emit( OpCodes::Br_S, endOfMthd );
// If this label is branched to (the failure case), load -1 onto the stack
// and fall through to the return opcode.
adderIL->MarkLabel( failed );
adderIL->Emit( OpCodes::Ldc_I4_M1 );
// The end of the method. If both values were less than 100, the
// correct result will return. If one of the arguments was greater
// than 100, the result will be -1.
adderIL->MarkLabel( endOfMthd );
adderIL->Emit( OpCodes::Ret );
return myTypeBldr->CreateType();
}
int main()
{
Type^ adderType = BuildAdderType();
Object^ addIns = Activator::CreateInstance( adderType );
array<Object^>^addParams = gcnew array<Object^>(2);
Console::Write( "Enter an integer value: " );
addParams[ 0 ] = Convert::ToInt32( Console::ReadLine() );
Console::Write( "Enter another integer value: " );
addParams[ 1 ] = Convert::ToInt32( Console::ReadLine() );
Console::WriteLine( "---" );
int adderResult = safe_cast<int>(adderType->InvokeMember( "DoAdd", BindingFlags::InvokeMethod, nullptr, addIns, addParams ));
if ( adderResult != -1 )
{
Console::WriteLine( " {0} + {1} = {2}", addParams[ 0 ], addParams[ 1 ], adderResult );
}
else
{
Console::WriteLine( "One of the integers to add was greater than 100!" );
}
}
Plattformen
Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0
Siehe auch
Referenz
ILGenerator-Klasse
ILGenerator-Member
System.Reflection.Emit-Namespace