ILGenerator.MarkLabel-Methode

Artikel
08/20/2007

Markiert die aktuelle Position des MSIL-Streams (Microsoft Intermediate Language) mit der angegebenen Sprungmarke.

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

Syntax

'Declaration
Public Overridable Sub MarkLabel ( _
    loc As Label _
)
'Usage
Dim instance As ILGenerator
Dim loc As Label

instance.MarkLabel(loc)

public virtual void MarkLabel (
    Label loc
)

public:
virtual void MarkLabel (
    Label loc
)

public void MarkLabel (
    Label loc
)

public function MarkLabel (
    loc : Label
)

Parameter

loc
Die Sprungmarke, für die ein Index festzulegen ist.

Ausnahmen

Ausnahmetyp	Bedingung
ArgumentException	loc stellt einen unzulässigen Index im Sprungmarkenarray dar. – oder – Es wurde bereits ein Index für loc definiert.

ArgumentException

loc stellt einen unzulässigen Index im Sprungmarkenarray dar.

– oder –

Es wurde bereits ein Index für loc definiert.

Hinweise

Eine Sprungmarke kann nur einmal definiert werden.

Beispiel

Das folgende Codebeispiel veranschaulicht die kontextabhängige Verwendung von MarkLabel zur Implementierung von IL-Verzweigungen in einer dynamischen Methode.

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

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}));  
              
   }

}

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 ) );
}

import System .* ;
import System.Threading .* ;
import System.Reflection .* ;
import System.Reflection.Emit .* ;

class DynamicJumpTableDemo
{
    public static Type BuildMyType()
    {
        AppDomain myDomain = System.Threading.Thread.GetDomain();
        AssemblyName myAsmName = new AssemblyName();
        myAsmName.set_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,
            String.class.ToType(),new Type[] { int.class.ToType() });
        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();
    } //BuildMyType    
   
   public static void main(String[] args)
   {
        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[]{(Int32)(theValue)}));
    } //main
} //DynamicJumpTableDemo

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.

Freigeben über

ILGenerator.MarkLabel-Methode

Syntax

Parameter

Ausnahmen

Hinweise

Beispiel

Plattformen

Versionsinformationen

.NET Framework

Siehe auch

Referenz

Zusätzliche Ressourcen