MethodBase.Invoke Método

Origem:

MethodBase.cs

Origem:

MethodBase.cs

Origem:

MethodBase.cs

public:
 virtual System::Object ^ Invoke(System::Object ^ obj, cli::array <System::Object ^> ^ parameters);

public:
 System::Object ^ Invoke(System::Object ^ obj, cli::array <System::Object ^> ^ parameters);

public virtual object Invoke (object obj, object[] parameters);

public object? Invoke (object? obj, object?[]? parameters);

public object Invoke (object obj, object[] parameters);

abstract member Invoke : obj * obj[] -> obj
override this.Invoke : obj * obj[] -> obj

member this.Invoke : obj * obj[] -> obj

Public Overridable Function Invoke (obj As Object, parameters As Object()) As Object

Public Function Invoke (obj As Object, parameters As Object()) As Object

Parâmetros

Retornos

Um objeto que contém o valor retornado do método invocado, ou null no caso de um construtor.

Implementações

Exceções

Exemplos

O exemplo de código a seguir demonstra a pesquisa de método dinâmico usando reflexão. Observe que você não pode usar o MethodInfo objeto da classe base para invocar o método substituído na classe derivada, pois a associação tardia não pode resolve substituições.

using namespace System;
using namespace System::Reflection;

public ref class MagicClass
{
private:
    int magicBaseValue;

public:
    MagicClass()
    {
        magicBaseValue = 9;
    }

    int ItsMagic(int preMagic)
    {
        return preMagic * magicBaseValue;
    }
};

public ref class TestMethodInfo
{
public:
    static void Main()
    {
        // Get the constructor and create an instance of MagicClass

        Type^ magicType = Type::GetType("MagicClass");
        ConstructorInfo^ magicConstructor = magicType->GetConstructor(Type::EmptyTypes);
        Object^ magicClassObject = magicConstructor->Invoke(gcnew array<Object^>(0));

        // Get the ItsMagic method and invoke with a parameter value of 100

        MethodInfo^ magicMethod = magicType->GetMethod("ItsMagic");
        Object^ magicValue = magicMethod->Invoke(magicClassObject, gcnew array<Object^>(1){100});

        Console::WriteLine("MethodInfo.Invoke() Example\n");
        Console::WriteLine("MagicClass.ItsMagic() returned: {0}", magicValue);
    }
};

int main()
{
    TestMethodInfo::Main();
}

// The example program gives the following output:
//
// MethodInfo.Invoke() Example
//
// MagicClass.ItsMagic() returned: 900

using System;
using System.Reflection;

public class MagicClass
{
    private int magicBaseValue;

    public MagicClass()
    {
        magicBaseValue = 9;
    }

    public int ItsMagic(int preMagic)
    {
        return preMagic * magicBaseValue;
    }
}

public class TestMethodInfo
{
    public static void Main()
    {
        // Get the constructor and create an instance of MagicClass

        Type magicType = Type.GetType("MagicClass");
        ConstructorInfo magicConstructor = magicType.GetConstructor(Type.EmptyTypes);
        object magicClassObject = magicConstructor.Invoke(new object[]{});

        // Get the ItsMagic method and invoke with a parameter value of 100

        MethodInfo magicMethod = magicType.GetMethod("ItsMagic");
        object magicValue = magicMethod.Invoke(magicClassObject, new object[]{100});

        Console.WriteLine("MethodInfo.Invoke() Example\n");
        Console.WriteLine("MagicClass.ItsMagic() returned: {0}", magicValue);
    }
}

// The example program gives the following output:
//
// MethodInfo.Invoke() Example
//
// MagicClass.ItsMagic() returned: 900

Imports System.Reflection

Public Class MagicClass
    Private magicBaseValue As Integer

    Public Sub New()
        magicBaseValue = 9
    End Sub

    Public Function ItsMagic(preMagic As Integer) As Integer
        Return preMagic * magicBaseValue
    End Function
End Class

Public Class TestMethodInfo
    Public Shared Sub Main()
        ' Get the constructor and create an instance of MagicClass

        Dim magicType As Type = Type.GetType("MagicClass")
        Dim magicConstructor As ConstructorInfo = magicType.GetConstructor(Type.EmptyTypes)
        Dim magicClassObject As Object = magicConstructor.Invoke(New Object(){})

        ' Get the ItsMagic method and invoke with a parameter value of 100

        Dim magicMethod As MethodInfo = magicType.GetMethod("ItsMagic")
        Dim magicValue As Object = magicMethod.Invoke(magicClassObject, New Object(){100})

        Console.WriteLine("MethodInfo.Invoke() Example" + Environment.NewLine)
        Console.WriteLine("MagicClass.ItsMagic() returned: {0}", magicValue)
    End Sub
End Class

' The example program gives the following output:
'
' MethodInfo.Invoke() Example
'
' MagicClass.ItsMagic() returned: 900

Comentários

Esse é um método de conveniência que chama a sobrecarga do Invoke(Object, BindingFlags, Binder, Object[], CultureInfo) método, passando Default para invokeAttr e null para binder e culture.

Se o método invocado gerar uma exceção, o Exception.GetBaseException método retornará a exceção de origem.

Para invocar um método estático usando seu MethodInfo objeto , passe null para obj.

Se um parâmetro do método refletido for um tipo de valor e o argumento correspondente em parameters for null, o runtime passará uma instância inicializada zero do tipo de valor.

Confira também

• BindingFlags
• Missing
• InvokeMember(String, BindingFlags, Binder, Object, Object[], ParameterModifier[], CultureInfo, String[])

Origem:

MethodBase.cs

Origem:

MethodBase.cs

Origem:

MethodBase.cs

public:
 abstract System::Object ^ Invoke(System::Object ^ obj, System::Reflection::BindingFlags invokeAttr, System::Reflection::Binder ^ binder, cli::array <System::Object ^> ^ parameters, System::Globalization::CultureInfo ^ culture);

public abstract object? Invoke (object? obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder? binder, object?[]? parameters, System.Globalization.CultureInfo? culture);

public abstract object Invoke (object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, object[] parameters, System.Globalization.CultureInfo culture);

abstract member Invoke : obj * System.Reflection.BindingFlags * System.Reflection.Binder * obj[] * System.Globalization.CultureInfo -> obj

Public MustOverride Function Invoke (obj As Object, invokeAttr As BindingFlags, binder As Binder, parameters As Object(), culture As CultureInfo) As Object

Parâmetros

Retornos

Um Object que contém o valor retornado do método invocado, ou null, no caso de um construtor, ou null, se o tipo de retorno do método for void. Antes de chamar o método ou o construtor, o Invoke verifica se o usuário tem permissão de acesso e verifica se os parâmetros são válidos.

Implementações

Exceções

Exemplos

O exemplo a seguir demonstra todos os membros da System.Reflection.Binder classe usando uma sobrecarga de Type.InvokeMember. O método CanConvertFrom privado localiza tipos compatíveis para um determinado tipo. Para obter outro exemplo de invocação de membros em um cenário de associação personalizada, consulte Carregando e usando tipos dinamicamente.

using namespace System;
using namespace System::Reflection;
using namespace System::Globalization;
using namespace System::Runtime::InteropServices;
public ref class MyBinder: public Binder
{
public:
   MyBinder()
      : Binder()
   {}

private:
   ref class BinderState
   {
   public:
      array<Object^>^args;
   };

public:
   virtual FieldInfo^ BindToField( BindingFlags bindingAttr, array<FieldInfo^>^match, Object^ value, CultureInfo^ culture ) override
   {
      if ( match == nullptr )
            throw gcnew ArgumentNullException( "match" );

      // Get a field for which the value parameter can be converted to the specified field type.
      for ( int i = 0; i < match->Length; i++ )
         if ( ChangeType( value, match[ i ]->FieldType, culture ) != nullptr )
                  return match[ i ];

      return nullptr;
   }

   virtual MethodBase^ BindToMethod( BindingFlags bindingAttr, array<MethodBase^>^match, array<Object^>^%args, array<ParameterModifier>^ modifiers, CultureInfo^ culture, array<String^>^names, [Out]Object^% state ) override
   {
      // Store the arguments to the method in a state Object*.
      BinderState^ myBinderState = gcnew BinderState;
      array<Object^>^arguments = gcnew array<Object^>(args->Length);
      args->CopyTo( arguments, 0 );
      myBinderState->args = arguments;
      state = myBinderState;
      if ( match == nullptr )
            throw gcnew ArgumentNullException;

      // Find a method that has the same parameters as those of the args parameter.
      for ( int i = 0; i < match->Length; i++ )
      {
         // Count the number of parameters that match.
         int count = 0;
         array<ParameterInfo^>^parameters = match[ i ]->GetParameters();

         // Go on to the next method if the number of parameters do not match.
         if ( args->Length != parameters->Length )
                  continue;

         // Match each of the parameters that the user expects the method to have.
         for ( int j = 0; j < args->Length; j++ )
         {
            // If the names parameter is not 0, then reorder args.
            if ( names != nullptr )
            {
               if ( names->Length != args->Length )
                              throw gcnew ArgumentException( "names and args must have the same number of elements." );

               for ( int k = 0; k < names->Length; k++ )
                  if ( String::Compare( parameters[ j ]->Name, names[ k ] ) == 0 )
                                    args[ j ] = myBinderState->args[ k ];
            }

            // Determine whether the types specified by the user can be converted to the parameter type.
            if ( ChangeType( args[ j ], parameters[ j ]->ParameterType, culture ) != nullptr )
                        count += 1;
            else
                        break;
         }
         if ( count == args->Length )
                  return match[ i ];
      }
      return nullptr;
   }

   virtual Object^ ChangeType( Object^ value, Type^ myChangeType, CultureInfo^ culture ) override
   {
      // Determine whether the value parameter can be converted to a value of type myType.
      if ( CanConvertFrom( value->GetType(), myChangeType ) )
         // Return the converted Object*.
         return Convert::ChangeType( value, myChangeType ); 
      else
         return nullptr;
   }

   virtual void ReorderArgumentArray( array<Object^>^%args, Object^ state ) override
   {
      // Return the args that had been reordered by BindToMethod.
      (safe_cast<BinderState^>(state))->args->CopyTo( args, 0 );
   }

   virtual MethodBase^ SelectMethod( BindingFlags bindingAttr, array<MethodBase^>^match, array<Type^>^types, array<ParameterModifier>^ modifiers ) override
   {
      if ( match == nullptr )
            throw gcnew ArgumentNullException( "match" );

      for ( int i = 0; i < match->Length; i++ )
      {
         // Count the number of parameters that match.
         int count = 0;
         array<ParameterInfo^>^parameters = match[ i ]->GetParameters();

         // Go on to the next method if the number of parameters do not match.
         if ( types->Length != parameters->Length )
                  continue;

         // Match each of the parameters that the user expects the method to have.
         for ( int j = 0; j < types->Length; j++ )
         {
            // Determine whether the types specified by the user can be converted to parameter type.
            if ( CanConvertFrom( types[ j ], parameters[ j ]->ParameterType ) )
                        count += 1;
            else
                        break;
         }
         // Determine whether the method has been found.
         if ( count == types->Length )
                  return match[ i ];
      }
      return nullptr;
   }

   virtual PropertyInfo^ SelectProperty( BindingFlags bindingAttr, array<PropertyInfo^>^match, Type^ returnType, array<Type^>^indexes, array<ParameterModifier>^ modifiers ) override
   {
      if ( match == nullptr )
            throw gcnew ArgumentNullException( "match" );

      for ( int i = 0; i < match->Length; i++ )
      {
         // Count the number of indexes that match.
         int count = 0;
         array<ParameterInfo^>^parameters = match[ i ]->GetIndexParameters();

         // Go on to the next property if the number of indexes do not match.
         if ( indexes->Length != parameters->Length )
                  continue;

         // Match each of the indexes that the user expects the property to have.
         for ( int j = 0; j < indexes->Length; j++ )
            // Determine whether the types specified by the user can be converted to index type.
            if ( CanConvertFrom( indexes[ j ], parameters[ j ]->ParameterType ) )
                        count += 1;
            else
                        break;

         // Determine whether the property has been found.
         if ( count == indexes->Length )
         {
            // Determine whether the return type can be converted to the properties type.
            if ( CanConvertFrom( returnType, match[ i ]->PropertyType ) )
                  return match[ i ];
            else
                  continue;
         }
      }
      return nullptr;
   }

private:

   // Determines whether type1 can be converted to type2. Check only for primitive types.
   bool CanConvertFrom( Type^ type1, Type^ type2 )
   {
      if ( type1->IsPrimitive && type2->IsPrimitive )
      {
         TypeCode typeCode1 = Type::GetTypeCode( type1 );
         TypeCode typeCode2 = Type::GetTypeCode( type2 );

         // If both type1 and type2 have the same type, return true.
         if ( typeCode1 == typeCode2 )
                  return true;

         // Possible conversions from Char follow.
         if ( typeCode1 == TypeCode::Char )
         {
            switch ( typeCode2 )
            {
               case TypeCode::UInt16:
                  return true;

               case TypeCode::UInt32:
                  return true;

               case TypeCode::Int32:
                  return true;

               case TypeCode::UInt64:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from Byte follow.
         if ( typeCode1 == TypeCode::Byte )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Char:
                  return true;

               case TypeCode::UInt16:
                  return true;

               case TypeCode::Int16:
                  return true;

               case TypeCode::UInt32:
                  return true;

               case TypeCode::Int32:
                  return true;

               case TypeCode::UInt64:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from SByte follow.
         if ( typeCode1 == TypeCode::SByte )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Int16:
                  return true;

               case TypeCode::Int32:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from UInt16 follow.
         if ( typeCode1 == TypeCode::UInt16 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::UInt32:
                  return true;

               case TypeCode::Int32:
                  return true;

               case TypeCode::UInt64:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from Int16 follow.
         if ( typeCode1 == TypeCode::Int16 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Int32:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from UInt32 follow.
         if ( typeCode1 == TypeCode::UInt32 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::UInt64:
                  return true;

               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from Int32 follow.
         if ( typeCode1 == TypeCode::Int32 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Int64:
                  return true;

               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from UInt64 follow.
         if ( typeCode1 == TypeCode::UInt64 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from Int64 follow.
         if ( typeCode1 == TypeCode::Int64 )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Single:
                  return true;

               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }

         // Possible conversions from Single follow.
         if ( typeCode1 == TypeCode::Single )
         {
            switch ( typeCode2 )
            {
               case TypeCode::Double:
                  return true;

               default:
                  return false;
            }
         }
      }

      return false;
   }

};

public ref class MyClass1
{
public:
   short myFieldB;
   int myFieldA;
   void MyMethod( long i, char k )
   {
      Console::WriteLine( "\nThis is MyMethod(long i, char k)" );
   }

   void MyMethod( long i, long j )
   {
      Console::WriteLine( "\nThis is MyMethod(long i, long j)" );
   }
};

int main()
{
   // Get the type of MyClass1.
   Type^ myType = MyClass1::typeid;

   // Get the instance of MyClass1.
   MyClass1^ myInstance = gcnew MyClass1;
   Console::WriteLine( "\nDisplaying the results of using the MyBinder binder.\n" );

   // Get the method information for MyMethod.
   array<Type^>^types = {short::typeid,short::typeid};
   MethodInfo^ myMethod = myType->GetMethod( "MyMethod", static_cast<BindingFlags>(BindingFlags::Public | BindingFlags::Instance), gcnew MyBinder, types, nullptr );
   Console::WriteLine( myMethod );

   // Invoke MyMethod.
   array<Object^>^obj = {32,32};
   myMethod->Invoke( myInstance, BindingFlags::InvokeMethod, gcnew MyBinder, obj, CultureInfo::CurrentCulture );
}

using System;
using System.Reflection;
using System.Globalization;

public class MyBinder : Binder
{
    public MyBinder() : base()
    {
    }
    private class BinderState
    {
        public object[] args;
    }
    public override FieldInfo BindToField(
        BindingFlags bindingAttr,
        FieldInfo[] match,
        object value,
        CultureInfo culture
        )
    {
        if(match == null)
            throw new ArgumentNullException("match");
        // Get a field for which the value parameter can be converted to the specified field type.
        for(int i = 0; i < match.Length; i++)
            if(ChangeType(value, match[i].FieldType, culture) != null)
                return match[i];
        return null;
    }
    public override MethodBase BindToMethod(
        BindingFlags bindingAttr,
        MethodBase[] match,
        ref object[] args,
        ParameterModifier[] modifiers,
        CultureInfo culture,
        string[] names,
        out object state
        )
    {
        // Store the arguments to the method in a state object.
        BinderState myBinderState = new BinderState();
        object[] arguments = new Object[args.Length];
        args.CopyTo(arguments, 0);
        myBinderState.args = arguments;
        state = myBinderState;
        if(match == null)
            throw new ArgumentNullException();
        // Find a method that has the same parameters as those of the args parameter.
        for(int i = 0; i < match.Length; i++)
        {
            // Count the number of parameters that match.
            int count = 0;
            ParameterInfo[] parameters = match[i].GetParameters();
            // Go on to the next method if the number of parameters do not match.
            if(args.Length != parameters.Length)
                continue;
            // Match each of the parameters that the user expects the method to have.
            for(int j = 0; j < args.Length; j++)
            {
                // If the names parameter is not null, then reorder args.
                if(names != null)
                {
                    if(names.Length != args.Length)
                        throw new ArgumentException("names and args must have the same number of elements.");
                    for(int k = 0; k < names.Length; k++)
                        if(String.Compare(parameters[j].Name, names[k].ToString()) == 0)
                            args[j] = myBinderState.args[k];
                }
                // Determine whether the types specified by the user can be converted to the parameter type.
                if(ChangeType(args[j], parameters[j].ParameterType, culture) != null)
                    count += 1;
                else
                    break;
            }
            // Determine whether the method has been found.
            if(count == args.Length)
                return match[i];
        }
        return null;
    }
    public override object ChangeType(
        object value,
        Type myChangeType,
        CultureInfo culture
        )
    {
        // Determine whether the value parameter can be converted to a value of type myType.
        if(CanConvertFrom(value.GetType(), myChangeType))
            // Return the converted object.
            return Convert.ChangeType(value, myChangeType);
        else
            // Return null.
            return null;
    }
    public override void ReorderArgumentArray(
        ref object[] args,
        object state
        )
    {
        // Return the args that had been reordered by BindToMethod.
        ((BinderState)state).args.CopyTo(args, 0);
    }
    public override MethodBase SelectMethod(
        BindingFlags bindingAttr,
        MethodBase[] match,
        Type[] types,
        ParameterModifier[] modifiers
        )
    {
        if(match == null)
            throw new ArgumentNullException("match");
        for(int i = 0; i < match.Length; i++)
        {
            // Count the number of parameters that match.
            int count = 0;
            ParameterInfo[] parameters = match[i].GetParameters();
            // Go on to the next method if the number of parameters do not match.
            if(types.Length != parameters.Length)
                continue;
            // Match each of the parameters that the user expects the method to have.
            for(int j = 0; j < types.Length; j++)
                // Determine whether the types specified by the user can be converted to parameter type.
                if(CanConvertFrom(types[j], parameters[j].ParameterType))
                    count += 1;
                else
                    break;
            // Determine whether the method has been found.
            if(count == types.Length)
                return match[i];
        }
        return null;
    }
    public override PropertyInfo SelectProperty(
        BindingFlags bindingAttr,
        PropertyInfo[] match,
        Type returnType,
        Type[] indexes,
        ParameterModifier[] modifiers
        )
    {
        if(match == null)
            throw new ArgumentNullException("match");
        for(int i = 0; i < match.Length; i++)
        {
            // Count the number of indexes that match.
            int count = 0;
            ParameterInfo[] parameters = match[i].GetIndexParameters();
            // Go on to the next property if the number of indexes do not match.
            if(indexes.Length != parameters.Length)
                continue;
            // Match each of the indexes that the user expects the property to have.
            for(int j = 0; j < indexes.Length; j++)
                // Determine whether the types specified by the user can be converted to index type.
                if(CanConvertFrom(indexes[j], parameters[j].ParameterType))
                    count += 1;
                else
                    break;
            // Determine whether the property has been found.
            if(count == indexes.Length)
                // Determine whether the return type can be converted to the properties type.
                if(CanConvertFrom(returnType, match[i].PropertyType))
                    return match[i];
                else
                    continue;
        }
        return null;
    }
    // Determines whether type1 can be converted to type2. Check only for primitive types.
    private bool CanConvertFrom(Type type1, Type type2)
    {
        if(type1.IsPrimitive && type2.IsPrimitive)
        {
            TypeCode typeCode1 = Type.GetTypeCode(type1);
            TypeCode typeCode2 = Type.GetTypeCode(type2);
            // If both type1 and type2 have the same type, return true.
            if(typeCode1 == typeCode2)
                return true;
            // Possible conversions from Char follow.
            if(typeCode1 == TypeCode.Char)
                switch(typeCode2)
                {
                    case TypeCode.UInt16 : return true;
                    case TypeCode.UInt32 : return true;
                    case TypeCode.Int32  : return true;
                    case TypeCode.UInt64 : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from Byte follow.
            if(typeCode1 == TypeCode.Byte)
                switch(typeCode2)
                {
                    case TypeCode.Char   : return true;
                    case TypeCode.UInt16 : return true;
                    case TypeCode.Int16  : return true;
                    case TypeCode.UInt32 : return true;
                    case TypeCode.Int32  : return true;
                    case TypeCode.UInt64 : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from SByte follow.
            if(typeCode1 == TypeCode.SByte)
                switch(typeCode2)
                {
                    case TypeCode.Int16  : return true;
                    case TypeCode.Int32  : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from UInt16 follow.
            if(typeCode1 == TypeCode.UInt16)
                switch(typeCode2)
                {
                    case TypeCode.UInt32 : return true;
                    case TypeCode.Int32  : return true;
                    case TypeCode.UInt64 : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from Int16 follow.
            if(typeCode1 == TypeCode.Int16)
                switch(typeCode2)
                {
                    case TypeCode.Int32  : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from UInt32 follow.
            if(typeCode1 == TypeCode.UInt32)
                switch(typeCode2)
                {
                    case TypeCode.UInt64 : return true;
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from Int32 follow.
            if(typeCode1 == TypeCode.Int32)
                switch(typeCode2)
                {
                    case TypeCode.Int64  : return true;
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from UInt64 follow.
            if(typeCode1 == TypeCode.UInt64)
                switch(typeCode2)
                {
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from Int64 follow.
            if(typeCode1 == TypeCode.Int64)
                switch(typeCode2)
                {
                    case TypeCode.Single : return true;
                    case TypeCode.Double : return true;
                    default              : return false;
                }
            // Possible conversions from Single follow.
            if(typeCode1 == TypeCode.Single)
                switch(typeCode2)
                {
                    case TypeCode.Double : return true;
                    default              : return false;
                }
        }
        return false;
    }
}
public class MyClass1
{
    public short myFieldB;
    public int myFieldA;
    public void MyMethod(long i, char k)
    {
        Console.WriteLine("\nThis is MyMethod(long i, char k)");
    }
    public void MyMethod(long i, long j)
    {
        Console.WriteLine("\nThis is MyMethod(long i, long j)");
    }
}
public class Binder_Example
{
    public static void Main()
    {
        // Get the type of MyClass1.
        Type myType = typeof(MyClass1);
        // Get the instance of MyClass1.
        MyClass1 myInstance = new MyClass1();
        Console.WriteLine("\nDisplaying the results of using the MyBinder binder.\n");
        // Get the method information for MyMethod.
        MethodInfo myMethod = myType.GetMethod("MyMethod", BindingFlags.Public | BindingFlags.Instance,
            new MyBinder(), new Type[] {typeof(short), typeof(short)}, null);
        Console.WriteLine(myMethod);
        // Invoke MyMethod.
        myMethod.Invoke(myInstance, BindingFlags.InvokeMethod, new MyBinder(), new Object[] {(int)32, (int)32}, CultureInfo.CurrentCulture);
    }
}

Imports System.Reflection
Imports System.Globalization

Public Class MyBinder
    Inherits Binder
    Public Sub New()
        MyBase.new()
    End Sub
    Private Class BinderState
        Public args() As Object
    End Class

    Public Overrides Function BindToField(ByVal bindingAttr As BindingFlags, ByVal match() As FieldInfo, ByVal value As Object, ByVal culture As CultureInfo) As FieldInfo
        If match Is Nothing Then
            Throw New ArgumentNullException("match")
        End If
        ' Get a field for which the value parameter can be converted to the specified field type.
        Dim i As Integer
        For i = 0 To match.Length - 1
            If Not (ChangeType(value, match(i).FieldType, culture) Is Nothing) Then
                Return match(i)
            End If
        Next i
        Return Nothing
    End Function 'BindToField

    Public Overrides Function BindToMethod(ByVal bindingAttr As BindingFlags, ByVal match() As MethodBase, ByRef args() As Object, ByVal modifiers() As ParameterModifier, ByVal culture As CultureInfo, ByVal names() As String, ByRef state As Object) As MethodBase
        ' Store the arguments to the method in a state object.
        Dim myBinderState As New BinderState()
        Dim arguments() As Object = New [Object](args.Length) {}
        args.CopyTo(arguments, 0)
        myBinderState.args = arguments
        state = myBinderState

        If match Is Nothing Then
            Throw New ArgumentNullException()
        End If
        ' Find a method that has the same parameters as those of args.
        Dim i As Integer
        For i = 0 To match.Length - 1
            ' Count the number of parameters that match.
            Dim count As Integer = 0
            Dim parameters As ParameterInfo() = match(i).GetParameters()
            ' Go on to the next method if the number of parameters do not match.
            If args.Length <> parameters.Length Then
                GoTo ContinueFori
            End If
            ' Match each of the parameters that the user expects the method to have.
            Dim j As Integer
            For j = 0 To args.Length - 1
                ' If names is not null, then reorder args.
                If Not (names Is Nothing) Then
                    If names.Length <> args.Length Then
                        Throw New ArgumentException("names and args must have the same number of elements.")
                    End If
                    Dim k As Integer
                    For k = 0 To names.Length - 1
                        If String.Compare(parameters(j).Name, names(k).ToString()) = 0 Then
                            args(j) = myBinderState.args(k)
                        End If
                    Next k
                End If ' Determine whether the types specified by the user can be converted to parameter type.
                If Not (ChangeType(args(j), parameters(j).ParameterType, culture) Is Nothing) Then
                    count += 1
                Else
                    Exit For
                End If
            Next j
            ' Determine whether the method has been found.
            If count = args.Length Then
                Return match(i)
            End If
ContinueFori:
        Next i
        Return Nothing
    End Function 'BindToMethod

    Public Overrides Function ChangeType(ByVal value As Object, ByVal myChangeType As Type, ByVal culture As CultureInfo) As Object
        ' Determine whether the value parameter can be converted to a value of type myType.
        If CanConvertFrom(value.GetType(), myChangeType) Then
            ' Return the converted object.
            Return Convert.ChangeType(value, myChangeType)
            ' Return null.
        Else
            Return Nothing
        End If
    End Function 'ChangeType

    Public Overrides Sub ReorderArgumentArray(ByRef args() As Object, ByVal state As Object)
        'Redimension the array to hold the state values.
        ReDim args(CType(state, BinderState).args.Length)
        ' Return the args that had been reordered by BindToMethod.
        CType(state, BinderState).args.CopyTo(args, 0)
    End Sub

    Public Overrides Function SelectMethod(ByVal bindingAttr As BindingFlags, ByVal match() As MethodBase, ByVal types() As Type, ByVal modifiers() As ParameterModifier) As MethodBase
        If match Is Nothing Then
            Throw New ArgumentNullException("match")
        End If
        Dim i As Integer
        For i = 0 To match.Length - 1
            ' Count the number of parameters that match.
            Dim count As Integer = 0
            Dim parameters As ParameterInfo() = match(i).GetParameters()
            ' Go on to the next method if the number of parameters do not match.
            If types.Length <> parameters.Length Then
                GoTo ContinueFori
            End If
            ' Match each of the parameters that the user expects the method to have.
            Dim j As Integer
            For j = 0 To types.Length - 1
                ' Determine whether the types specified by the user can be converted to parameter type.
                If CanConvertFrom(types(j), parameters(j).ParameterType) Then
                    count += 1
                Else
                    Exit For
                End If
            Next j ' Determine whether the method has been found.
            If count = types.Length Then
                Return match(i)
            End If
ContinueFori:
        Next i
        Return Nothing
    End Function 'SelectMethod
    Public Overrides Function SelectProperty(ByVal bindingAttr As BindingFlags, ByVal match() As PropertyInfo, ByVal returnType As Type, ByVal indexes() As Type, ByVal modifiers() As ParameterModifier) As PropertyInfo
        If match Is Nothing Then
            Throw New ArgumentNullException("match")
        End If
        Dim i As Integer
        For i = 0 To match.Length - 1
            ' Count the number of indexes that match.
            Dim count As Integer = 0
            Dim parameters As ParameterInfo() = match(i).GetIndexParameters()

            ' Go on to the next property if the number of indexes do not match.
            If indexes.Length <> parameters.Length Then
                GoTo ContinueFori
            End If
            ' Match each of the indexes that the user expects the property to have.
            Dim j As Integer
            For j = 0 To indexes.Length - 1
                ' Determine whether the types specified by the user can be converted to index type.
                If CanConvertFrom(indexes(j), parameters(j).ParameterType) Then
                    count += 1
                Else
                    Exit For
                End If
            Next j ' Determine whether the property has been found.
            If count = indexes.Length Then
                ' Determine whether the return type can be converted to the properties type.
                If CanConvertFrom(returnType, match(i).PropertyType) Then
                    Return match(i)
                Else
                    GoTo ContinueFori
                End If
            End If
ContinueFori:
        Next i
        Return Nothing
    End Function 'SelectProperty

    ' Determine whether type1 can be converted to type2. Check only for primitive types.
    Private Function CanConvertFrom(ByVal type1 As Type, ByVal type2 As Type) As Boolean
        If type1.IsPrimitive And type2.IsPrimitive Then
            Dim typeCode1 As TypeCode = Type.GetTypeCode(type1)
            Dim typeCode2 As TypeCode = Type.GetTypeCode(type2)
            ' If both type1 and type2 have same type, return true.
            If typeCode1 = typeCode2 Then
                Return True
            End If ' Possible conversions from Char follow.
            If typeCode1 = TypeCode.Char Then
                Select Case typeCode2
                    Case TypeCode.UInt16
                        Return True
                    Case TypeCode.UInt32
                        Return True
                    Case TypeCode.Int32
                        Return True
                    Case TypeCode.UInt64
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from Byte follow.
            If typeCode1 = TypeCode.Byte Then
                Select Case typeCode2
                    Case TypeCode.Char
                        Return True
                    Case TypeCode.UInt16
                        Return True
                    Case TypeCode.Int16
                        Return True
                    Case TypeCode.UInt32
                        Return True
                    Case TypeCode.Int32
                        Return True
                    Case TypeCode.UInt64
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from SByte follow.
            If typeCode1 = TypeCode.SByte Then
                Select Case typeCode2
                    Case TypeCode.Int16
                        Return True
                    Case TypeCode.Int32
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from UInt16 follow.
            If typeCode1 = TypeCode.UInt16 Then
                Select Case typeCode2
                    Case TypeCode.UInt32
                        Return True
                    Case TypeCode.Int32
                        Return True
                    Case TypeCode.UInt64
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from Int16 follow.
            If typeCode1 = TypeCode.Int16 Then
                Select Case typeCode2
                    Case TypeCode.Int32
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from UInt32 follow.
            If typeCode1 = TypeCode.UInt32 Then
                Select Case typeCode2
                    Case TypeCode.UInt64
                        Return True
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from Int32 follow.
            If typeCode1 = TypeCode.Int32 Then
                Select Case typeCode2
                    Case TypeCode.Int64
                        Return True
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from UInt64 follow.
            If typeCode1 = TypeCode.UInt64 Then
                Select Case typeCode2
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from Int64 follow.
            If typeCode1 = TypeCode.Int64 Then
                Select Case typeCode2
                    Case TypeCode.Single
                        Return True
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If ' Possible conversions from Single follow.
            If typeCode1 = TypeCode.Single Then
                Select Case typeCode2
                    Case TypeCode.Double
                        Return True
                    Case Else
                        Return False
                End Select
            End If
        End If
        Return False
    End Function 'CanConvertFrom
End Class


Public Class MyClass1
    Public myFieldB As Short
    Public myFieldA As Integer

    Public Overloads Sub MyMethod(ByVal i As Long, ByVal k As Char)
        Console.WriteLine(ControlChars.NewLine & "This is MyMethod(long i, char k).")
    End Sub

    Public Overloads Sub MyMethod(ByVal i As Long, ByVal j As Long)
        Console.WriteLine(ControlChars.NewLine & "This is MyMethod(long i, long j).")
    End Sub
End Class


Public Class Binder_Example
    Public Shared Sub Main()
        ' Get the type of MyClass1.
        Dim myType As Type = GetType(MyClass1)
        ' Get the instance of MyClass1.
        Dim myInstance As New MyClass1()
        Console.WriteLine(ControlChars.Cr & "Displaying the results of using the MyBinder binder.")
        Console.WriteLine()
        ' Get the method information for MyMethod.
        Dim myMethod As MethodInfo = myType.GetMethod("MyMethod", BindingFlags.Public Or BindingFlags.Instance, New MyBinder(), New Type() {GetType(Short), GetType(Short)}, Nothing)
        Console.WriteLine(MyMethod)
        ' Invoke MyMethod.
        myMethod.Invoke(myInstance, BindingFlags.InvokeMethod, New MyBinder(), New [Object]() {CInt(32), CInt(32)}, CultureInfo.CurrentCulture)
    End Sub
End Class

Comentários

Esse método invoca dinamicamente o método refletido por essa instância em obje passa os parâmetros especificados. Se o método for estático, o obj parâmetro será ignorado. Para métodos não estáticos, obj deve ser uma instância de uma classe que herda ou declara o método e deve ser do mesmo tipo que essa classe. Se o método não tiver parâmetros, o valor de parameters deverá ser null. Caso contrário, o número, o tipo e a ordem dos elementos em parameters devem ser idênticos ao número, ao tipo e à ordem dos parâmetros para o método refletido por essa instância.

Você não pode omitir parâmetros opcionais em chamadas para Invoke. Para invocar um método e omitir parâmetros opcionais, chame Type.InvokeMember em vez disso.

Para parâmetros primitivos pass-by-value, a ampliação normal é executada (Int16 –> Int32, por exemplo). Para parâmetros de referência pass-by-value, a ampliação de referência normal é permitida (classe derivada para classe base e classe base para o tipo de interface). No entanto, para parâmetros primitivos pass-by-reference, os tipos devem corresponder exatamente. Para parâmetros de referência pass-by-reference, a ampliação normal ainda se aplica.

Por exemplo, se o método refletido por essa instância for declarado como public boolean Compare(String a, String b), parameters deverá ser uma matriz de Objects com comprimento 2, de modo que parameters[0] = new Object("SomeString1") and parameters[1] = new Object("SomeString2").

Se um parâmetro do método atual for um tipo de valor e o argumento correspondente em parameters for null, o runtime passará uma instância inicializada zero do tipo de valor.

A reflexão usa a pesquisa de método dinâmico ao invocar métodos virtuais. Por exemplo, suponha que a classe B herde da classe A e implemente um método virtual chamado M. Agora suponha que você tenha um MethodInfo objeto que representa M na classe A. Se você usar o Invoke método para invocar M em um objeto do tipo B, a reflexão usará a implementação fornecida pela classe B. Mesmo que o objeto do tipo B seja convertido em A, a implementação fornecida pela classe B será usada (consulte o exemplo de código abaixo).

Por outro lado, se o método não for virtual, a reflexão usará a implementação fornecida pelo tipo do qual o MethodInfo foi obtido, independentemente do tipo do objeto passado como destino.

As restrições de acesso são ignoradas para código totalmente confiável. Ou seja, construtores privados, métodos, campos e propriedades podem ser acessados e invocados por meio de reflexão sempre que o código for totalmente confiável.

Se o método invocado gerar uma exceção, o Exception.GetBaseException método retornará a exceção de origem.

Confira também

• InvokeMember(String, BindingFlags, Binder, Object, Object[], ParameterModifier[], CultureInfo, String[])
• Carregando e usando tipos dinamicamente