ILGenerator.BeginCatchBlock メソッド

.NET Framework クラス ライブラリ リファレンス

ILGenerator.BeginCatchBlock メソッド

catch ブロックを開始します。

名前空間: System.Reflection.Emit
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Overridable Sub BeginCatchBlock
 ( _
    exceptionType As Type _
)

Visual Basic (使用法)

Dim instance As ILGenerator
Dim exceptionType As Type

instance.BeginCatchBlock(exceptionType)

C#

public virtual void BeginCatchBlock (
    Type exceptionType
)

C++

public:
virtual void BeginCatchBlock (
    Type^ exceptionType
)

J#

public void BeginCatchBlock (
    Type exceptionType
)

JScript

public function BeginCatchBlock (
    exceptionType : Type
)

パラメータ

exceptionType

例外を表す Type オブジェクト。

例外

例外の種類	条件
ArgumentException	catch ブロックが、フィルタ処理された例外の内側にあります。
ArgumentNullException	exceptionType が null 参照 (Visual Basic では Nothing) で、この catch ブロックが出現するまで、finally ブロックを実行することを示す値を例外フィルタ ブロックが返していません。
NotSupportedException	生成されている MSIL (Microsoft intermediate language) は、現在例外ブロックに含まれていません。

解説

現在の例外ブロックの末尾に分岐命令を生成します。

メモ
フィルタ例外ブロックが constant exception_execute_handler (共通言語基盤命令セットのドキュメントを参照してください) を返した場合、BeginCatchBlock の引数は検証されません。

使用例

BeginCatchBlock メソッドの実際の使用方法については、次のコード例を参照してください。

Visual Basic

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

 _

Class ILThrowExceptionDemo
   
   
   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 throw an
 exception.
      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 exCtorInfo As ConstructorInfo = GetType(OverflowException).GetConstructor(
 _
                            New Type() {GetType(String)})
      Dim exToStrMI As MethodInfo = GetType(OverflowException).GetMethod("ToString")
      Dim writeLineMI As MethodInfo = GetType(Console).GetMethod("WriteLine",
 _
                            New Type() {GetType(String),
 _
                                    GetType(Object)})
      
      Dim tmp1 As LocalBuilder = adderIL.DeclareLocal(GetType(Integer))
      Dim tmp2 As LocalBuilder = adderIL.DeclareLocal(GetType(OverflowException))
      
      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 throws an exception.

      Dim exBlock As Label = adderIL.BeginExceptionBlock()
      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.Stloc_S, tmp1)
      adderIL.Emit(OpCodes.Br_S, endOfMthd)
      
      ' If one of the arguments was greater than 100, we need to throw
 an
      ' exception. We'll use "OverflowException" with a customized
 message.
      ' First, we load our message onto the stack, and then create a
 new
      ' exception object using the constructor overload that accepts
 a

      ' string message.
      adderIL.MarkLabel(failed)
      adderIL.Emit(OpCodes.Ldstr, "Cannot accept values over 100
 for add.")
      adderIL.Emit(OpCodes.Newobj, exCtorInfo)
      
      ' We're going to need to refer to that exception object later,
 so let's
      ' store it in a temporary variable. Since the store function pops
 the
      ' the value/reference off the stack, and we'll need it to throw
 the
      ' exception, we will subsequently load it back onto the stack
 as well.

      adderIL.Emit(OpCodes.Stloc_S, tmp2)
      adderIL.Emit(OpCodes.Ldloc_S, tmp2)
      
      ' Throw the exception currently atop the stack.

      adderIL.ThrowException(GetType(OverflowException))
      
      ' Start the catch block.

      adderIL.BeginCatchBlock(GetType(OverflowException))
      
      ' First, we'll load a "wrapper" string, and then perform
 a 
      ' late-bound call to the ToString() method of OverflowException
,
      ' passing it the exception object we stored in local variable
 tmp2.

      adderIL.Emit(OpCodes.Ldstr, "{0}")
      adderIL.Emit(OpCodes.Ldloc_S, tmp2)
      adderIL.EmitCall(OpCodes.Callvirt, exToStrMI, Nothing)
      
      ' Now, we should have the "wrapper" string atop the
 stack,
      ' along with the string result of the ToString() call. All
      ' conditions are met to call WriteLine(string, object).

      adderIL.EmitCall(OpCodes.Call, writeLineMI, Nothing)
      
      ' Since our function has to return an integer value, we'll load
 -1 onto
      ' the stack to indicate an error, and store it in local variable
 tmp1.

      adderIL.Emit(OpCodes.Ldc_I4_M1)
      adderIL.Emit(OpCodes.Stloc_S, tmp1)
      
      ' End the exception handling block.

      adderIL.EndExceptionBlock()
      
      ' The end of the method. If no exception was thrown, the correct
 value
      ' will be saved in tmp1. If an exception was thrown, tmp1 will
 be equal
      ' to -1. Either way, we'll load the value of tmp1 onto the stack
 and return.

      adderIL.MarkLabel(endOfMthd)
      adderIL.Emit(OpCodes.Ldloc_S, tmp1)
      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("If either integer was > 100, an exception
 will be thrown.")
      Console.WriteLine("---")
      
      Console.WriteLine("{0} + {1} = {2}", addParams(0),
 addParams(1), _
            adderType.InvokeMember("DoAdd", _
                        BindingFlags.InvokeMethod, _
                        Nothing, addIns, addParams))

   End Sub 'Main

End Class 'ILThrowExceptionDemo

C#

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

class ILThrowExceptionDemo {

   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 throw an exception.

    MethodBuilder adderBldr = myTypeBldr.DefineMethod("DoAdd",
                            MethodAttributes.Public |
                               MethodAttributes.Static,
                               typeof(int),
                               adderParams);
    ILGenerator adderIL = adderBldr.GetILGenerator();

    // 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.

    ConstructorInfo exCtorInfo = typeof(OverflowException).GetConstructor(
                                new Type[]
                                {typeof(string)});
    MethodInfo exToStrMI = typeof(OverflowException).GetMethod("ToString");
    MethodInfo writeLineMI = typeof(Console).GetMethod("WriteLine",
                                new Type[] 
                                {typeof(string),
                                 typeof(object)});
                                                                   
    LocalBuilder tmp1 = adderIL.DeclareLocal(typeof(int));   
 
    LocalBuilder tmp2 = adderIL.DeclareLocal(typeof(OverflowException));

    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 throws an exception.

    Label exBlock = adderIL.BeginExceptionBlock();
    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.Stloc_S, tmp1);
    adderIL.Emit(OpCodes.Br_S, endOfMthd);

    // If one of the arguments was greater than 100, we need to throw
 an
    // exception. We'll use "OverflowException" with a customized
 message.
    // First, we load our message onto the stack, and then create a
 new
    // exception object using the constructor overload that accepts
 a
    // string message.

    adderIL.MarkLabel(failed);
    adderIL.Emit(OpCodes.Ldstr, "Cannot accept values over 100 for
 add.");
    adderIL.Emit(OpCodes.Newobj, exCtorInfo);

    // We're going to need to refer to that exception object later,
 so let's
    // store it in a temporary variable. Since the store function pops
 the
    // the value/reference off the stack, and we'll need it to throw
 the
    // exception, we will subsequently load it back onto the stack as
 well.

    adderIL.Emit(OpCodes.Stloc_S, tmp2);
    adderIL.Emit(OpCodes.Ldloc_S, tmp2);

    // Throw the exception currently atop the stack.

    adderIL.ThrowException(typeof(OverflowException));
        
    // Start the catch block.

    adderIL.BeginCatchBlock(typeof(OverflowException));

    // First, we'll load a "wrapper" string, and then perform
 a 
    // late-bound call to the ToString() method of OverflowException
,
    // passing it the exception object we stored in local variable tmp2.

    adderIL.Emit(OpCodes.Ldstr, "{0}");
    adderIL.Emit(OpCodes.Ldloc_S, tmp2);
    adderIL.EmitCall(OpCodes.Callvirt, exToStrMI, null);

    // Now, we should have the "wrapper" string atop the stack
,
    // along with the string result of the ToString() call. All
    // conditions are met to call WriteLine(string, object).

    adderIL.EmitCall(OpCodes.Call, writeLineMI, null);

    // Since our function has to return an integer value, we'll load
 -1 onto
    // the stack to indicate an error, and store it in local variable
 tmp1.

    adderIL.Emit(OpCodes.Ldc_I4_M1);
    adderIL.Emit(OpCodes.Stloc_S, tmp1);

    // End the exception handling block.

    adderIL.EndExceptionBlock();    

    // The end of the method. If no exception was thrown, the correct
 value
    // will be saved in tmp1. If an exception was thrown, tmp1 will
 be equal
    // to -1. Either way, we'll load the value of tmp1 onto the stack
 and return.

    adderIL.MarkLabel(endOfMthd);
    adderIL.Emit(OpCodes.Ldloc_S, tmp1);
    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("If either integer was > 100, an exception will be
 thrown.");
    Console.WriteLine("---");

    Console.WriteLine("{0} + {1} = {2}",
                addParams[0], addParams[1],
                adderType.InvokeMember("DoAdd",
                    BindingFlags.InvokeMethod,
                    null,
                    addIns,
                    addParams)); 
            
   }

}

C++

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 throw an exception.
   MethodBuilder^ adderBldr = myTypeBldr->DefineMethod( "DoAdd", static_cast<MethodAttributes>(MethodAttributes::Public
 | MethodAttributes::Static), int::typeid, adderParams );
   ILGenerator^ adderIL = adderBldr->GetILGenerator();
   
   // 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.
   array<Type^>^temp0 = {String::typeid};
   ConstructorInfo^ exCtorInfo = OverflowException::typeid->GetConstructor( temp0
 );
   MethodInfo^ exToStrMI = OverflowException::typeid->GetMethod( "ToString"
 );
   array<Type^>^temp1 = {String::typeid,Object::typeid};
   MethodInfo^ writeLineMI = Console::typeid->GetMethod( "WriteLine",
 temp1 );
   LocalBuilder^ tmp1 = adderIL->DeclareLocal( int::typeid
 );
   LocalBuilder^ tmp2 = adderIL->DeclareLocal( OverflowException::typeid );
   Label failed = adderIL->DefineLabel();
   Label endOfMthd = adderIL->DefineLabel();
   
   // First, load argument 0 and the integer value of S"100"
 onto the
   // stack. If arg0 > 100, branch to the label S"failed",
 which is marked
   // as the address of the block that throws an exception.
   Label exBlock = adderIL->BeginExceptionBlock();
   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 S"failed." Otherwise, fall through and perform
 the addition,
   // branching unconditionally to the instruction at the label S"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::Stloc_S, tmp1 );
   adderIL->Emit( OpCodes::Br_S, endOfMthd );
   
   // If one of the arguments was greater than 100, we need to throw
 an
   // exception. We'll use "OverflowException" with a customized
 message.
   // First, we load our message onto the stack, and then create a new
   // exception Object using the constructor overload that accepts a
   // String* message.
   adderIL->MarkLabel( failed );
   adderIL->Emit( OpCodes::Ldstr, "Cannot accept values over 100 for
 add." );
   adderIL->Emit( OpCodes::Newobj, exCtorInfo );
   
   // We're going to need to refer to that exception Object later, so
 let's
   // store it in a temporary variable. Since the store function pops
 the
   // the value/reference off the stack, and we'll need it to throw
 the
   // exception, we will subsequently load it back onto the stack as
 well.
   adderIL->Emit( OpCodes::Stloc_S, tmp2 );
   adderIL->Emit( OpCodes::Ldloc_S, tmp2 );
   
   // Throw the exception currently atop the stack.
   adderIL->ThrowException( OverflowException::typeid );
   
   // Start the catch block.
   adderIL->BeginCatchBlock( OverflowException::typeid );
   
   // First, we'll load a "wrapper" String, and then perform
 a
   // late-bound call to the ToString() method of OverflowException
,
   // passing it the exception Object we stored in local variable tmp2.
   adderIL->Emit( OpCodes::Ldstr, " {0}" );
   adderIL->Emit( OpCodes::Ldloc_S, tmp2 );
   adderIL->EmitCall( OpCodes::Callvirt, exToStrMI, nullptr );
   
   // Now, we should have the "wrapper" String atop the stack
,
   // along with the String result of the ToString() call. All
   // conditions are met to call WriteLine(String*, Object*).
   adderIL->EmitCall( OpCodes::Call, writeLineMI, nullptr );
   
   // Since our function has to return an integer value, we'll load
 -1 onto
   // the stack to indicate an error, and store it in local variable
 tmp1.
   adderIL->Emit( OpCodes::Ldc_I4_M1 );
   adderIL->Emit( OpCodes::Stloc_S, tmp1 );
   
   // End the exception handling block.
   adderIL->EndExceptionBlock();
   
   // The end of the method. If no exception was thrown, the correct
 value
   // will be saved in tmp1. If an exception was thrown, tmp1 will be
 equal
   // to -1. Either way, we'll load the value of tmp1 onto the stack
 and return.
   adderIL->MarkLabel( endOfMthd );
   adderIL->Emit( OpCodes::Ldloc_S, tmp1 );
   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( "If either integer was > 100, an exception will be
 thrown." );
   Console::WriteLine( "---" );
   Console::WriteLine( " {0} + {1} = {2}", addParams[ 0 ], addParams[ 1
 ], adderType->InvokeMember( "DoAdd", BindingFlags::InvokeMethod, nullptr,
 addIns, addParams ) );
}

プラットフォーム

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

開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0

参照

関連項目
ILGenerator クラス
ILGenerator メンバ
System.Reflection.Emit 名前空間