ILGenerator.DefineLabel Metoda

Definice

Obor názvů:

System.Reflection.Emit

Sestavení:

System.Reflection.Emit.ILGeneration.dll

Zdroj:

ILGenerator.cs

Deklaruje nový popisek.

public:
 abstract System::Reflection::Emit::Label DefineLabel();

public abstract System.Reflection.Emit.Label DefineLabel ();

abstract member DefineLabel : unit -> System.Reflection.Emit.Label

Public MustOverride Function DefineLabel () As Label

Návraty

Label

Nový popisek, který lze použít jako token pro větvení.

Příklady

Následující ukázka kódu ukazuje kontextové použití DefineLabel metody.

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!" );
   }
}

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!");
    }		
   }
}

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
End Class

Poznámky

Pokud chcete nastavit pozici popisku ve streamu, musíte volat MarkLabel. Pokud to neuděláte, dojde k zavolání ArgumentExceptionTypeBuilder.CreateType .

Jedná se pouze o token, který ještě nepředstavuje žádné konkrétní umístění v rámci streamu.