ILGenerator.DefineLabel 方法

定义

命名空间:

System.Reflection.Emit

程序集:

System.Reflection.Emit.ILGeneration.dll

程序集:

mscorlib.dll

程序集:

netstandard.dll

声明新标签。

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

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

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

Public Overridable Function DefineLabel () As Label

返回

Label

可用作分支令牌的新标签。

示例

下面的代码示例演示方法 DefineLabel 的上下文用法。

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

注解

若要设置流中标签的位置，必须调用 MarkLabel。 失败会导致 ArgumentException 调用时间 TypeBuilder.CreateType 。

这只是一个令牌，尚不表示流中的任何特定位置。