Como conectar um delegado usando a reflexão

Artigo
04/03/2024

Quando você usa a reflexão para carregar e executar assemblies, não pode usar recursos de linguagem como o operador += do C# ou a instrução AddHandler do Visual Basic para conectar eventos. Os procedimentos a seguir mostram como conectar um método existente a um evento obtendo todos os tipos necessários por meio de reflexão e como criar um método dinâmico usando a emissão de reflexão e conectá-lo a um evento.

Observação

Para encontrar outra maneira de conectar um delegado manipulador de evento, consulte o exemplo de código para o método AddEventHandler da classe EventInfo.

Para conectar um delegado usando reflexão

Carregue um assembly que contém o tipo que gera eventos. Os assemblies normalmente são carregados com o método Assembly.Load. Para manter esse exemplo simples, um formulário derivado no assembly atual é usado, portanto, o método GetExecutingAssembly é usado para carregar o assembly atual.
```
Assembly^ assem = Example::typeid->Assembly;
```
```
Assembly assem = typeof(Example).Assembly;
```
```
Dim assem As Assembly = GetType(Example).Assembly
```
Obtenha um objeto Type que representa o tipo e crie uma instância do tipo. O método CreateInstance(Type) é usado no código a seguir porque o formulário tem um construtor sem parâmetros. Há várias outras sobrecargas do método CreateInstance que poderão ser usadas se o tipo sendo criado não tiver um construtor sem parâmetros. A nova instância é armazenada como o tipo Object para manter a ficção de que nada é conhecido sobre o assembly. (A reflexão permite que você obtenha os tipos em um assembly sem saber seus nomes com antecedência.)
```
Type^ tExForm = assem->GetType("ExampleForm");
Object^ exFormAsObj = Activator::CreateInstance(tExForm);
```
```
Type tExForm = assem.GetType("ExampleForm");
Object exFormAsObj = Activator.CreateInstance(tExForm);
```
```
Dim tExForm As Type = assem.GetType("ExampleForm")
Dim exFormAsObj As Object = _
    Activator.CreateInstance(tExForm)
```

Obtenha um objeto EventInfo que representa o evento e use a propriedade EventHandlerType para obter o tipo de delegado usado para manipular o evento. No código a seguir, é obtido um EventInfo para o evento Click.

EventInfo^ evClick = tExForm->GetEvent("Click");
Type^ tDelegate = evClick->EventHandlerType;

EventInfo evClick = tExForm.GetEvent("Click");
Type tDelegate = evClick.EventHandlerType;

Dim evClick As EventInfo = tExForm.GetEvent("Click")
Dim tDelegate As Type = evClick.EventHandlerType

Obtenha um objeto MethodInfo que representa o método que manipula o evento. O código de programa completo na seção Exemplo posteriormente neste artigo contém um método que corresponde à assinatura do delegado EventHandler, que manipula o evento Click, mas você também pode gerar métodos dinâmicos no tempo de execução. Para obter detalhes, consulte o procedimento que acompanha esse artigo para gerar um manipulador de eventos em tempo de execução usando um método dinâmico.
```
MethodInfo^ miHandler =
    Type::GetType("Example")->GetMethod("LuckyHandler",
        BindingFlags::NonPublic | BindingFlags::Instance);
```
```
MethodInfo miHandler =
    typeof(Example).GetMethod("LuckyHandler",
        BindingFlags.NonPublic | BindingFlags.Instance);
```
```
Dim miHandler As MethodInfo = _
    GetType(Example).GetMethod("LuckyHandler", _
        BindingFlags.NonPublic Or BindingFlags.Instance)
```
Crie uma instância do delegado usando o método CreateDelegate. Esse método é estático (Shared no Visual Basic), portanto, o tipo de delegado deve ser fornecido. O uso das sobrecargas de CreateDelegate que utilizam um MethodInfo é recomendado.
```
Delegate^ d = Delegate::CreateDelegate(tDelegate, this, miHandler);
```
```
Delegate d = Delegate.CreateDelegate(tDelegate, this, miHandler);
```
```
Dim d As [Delegate] = _
    [Delegate].CreateDelegate(tDelegate, Me, miHandler)
```
Obtenha o método do acessador add e invoque-o para conectar o evento. Todos os eventos têm um acessador add e um acessador remove, que estão ocultos pela sintaxe de linguagens de alto nível. Por exemplo, o C# usa o operador += para conectar eventos e o Visual Basic usa a instrução AddHandler. O código a seguir obtém o acessador add do evento Click e o invoca com associação tardia, passando a instância do delegado. Os argumentos devem ser passados como uma matriz.
```
MethodInfo^ addHandler = evClick->GetAddMethod();
array<Object^>^ addHandlerArgs = { d };
addHandler->Invoke(exFormAsObj, addHandlerArgs);
```
```
MethodInfo addHandler = evClick.GetAddMethod();
Object[] addHandlerArgs = { d };
addHandler.Invoke(exFormAsObj, addHandlerArgs);
```
```
Dim miAddHandler As MethodInfo = evClick.GetAddMethod()
Dim addHandlerArgs() As Object = {d}
miAddHandler.Invoke(exFormAsObj, addHandlerArgs)
```
Teste o evento. O código a seguir mostra o formulário definido no exemplo de código. Clicar no formulário invoca o manipulador de eventos.
```
Application::Run((Form^) exFormAsObj);
```
```
Application.Run((Form) exFormAsObj);
```
```
Application.Run(CType(exFormAsObj, Form))
```

Gerar um manipulador de eventos em tempo de execução usando um método dinâmico

Os métodos do manipulador de eventos podem ser gerados em tempo de execução, usando métodos dinâmicos leves e a emissão de reflexão. Para criar um manipulador de eventos, são necessários o tipo de retorno e os tipos de parâmetro do delegado. Eles podem ser obtidos examinando o método Invoke do delegado. O código a seguir usa os métodos GetDelegateReturnType e GetDelegateParameterTypes para obter essas informações. O código para esses métodos pode ser encontrado na seção Exemplo, posteriormente neste artigo.

Não é necessário nomear um DynamicMethod, portanto, a cadeia de caracteres vazia pode ser usada. No código a seguir, o último argumento associa o método dinâmico ao tipo atual, concedendo ao delegado o acesso a todos os membros públicos e privados da classe Example.

Type^ returnType = GetDelegateReturnType(tDelegate);
if (returnType != void::typeid)
    throw gcnew ApplicationException("Delegate has a return type.");
    
DynamicMethod^ handler =
    gcnew DynamicMethod("",
                      nullptr,
                      GetDelegateParameterTypes(tDelegate),
                      Example::typeid);

Type returnType = GetDelegateReturnType(tDelegate);
if (returnType != typeof(void))
    throw new ArgumentException("Delegate has a return type.", nameof(d));

DynamicMethod handler =
    new DynamicMethod("",
                      null,
                      GetDelegateParameterTypes(tDelegate),
                      typeof(Example));

Dim returnType As Type = GetDelegateReturnType(tDelegate)
If returnType IsNot GetType(Void) Then
    Throw New ArgumentException("Delegate has a return type.", NameOf(d))
End If

Dim handler As New DynamicMethod( _
    "", _
    Nothing, _
    GetDelegateParameterTypes(tDelegate), _
    GetType(Example) _
)

Gere um corpo de método. Esse método carrega uma cadeia de caracteres, chama a sobrecarga do método MessageBox.Show que usa uma cadeia de caracteres, exibe o valor retornado da pilha (porque o manipulador não tem nenhum tipo de retorno) e retorna. Para saber mais sobre a emissão de métodos dinâmicos, consulte Como definir e executar métodos dinâmicos.

ILGenerator^ ilgen = handler->GetILGenerator();

array<Type^>^ showParameters = { String::typeid };
MethodInfo^ simpleShow =
    MessageBox::typeid->GetMethod("Show", showParameters);

ilgen->Emit(OpCodes::Ldstr,
    "This event handler was constructed at run time.");
ilgen->Emit(OpCodes::Call, simpleShow);
ilgen->Emit(OpCodes::Pop);
ilgen->Emit(OpCodes::Ret);

ILGenerator ilgen = handler.GetILGenerator();

Type[] showParameters = { typeof(String) };
MethodInfo simpleShow =
    typeof(MessageBox).GetMethod("Show", showParameters);

ilgen.Emit(OpCodes.Ldstr,
    "This event handler was constructed at run time.");
ilgen.Emit(OpCodes.Call, simpleShow);
ilgen.Emit(OpCodes.Pop);
ilgen.Emit(OpCodes.Ret);

Dim ilgen As ILGenerator = handler.GetILGenerator()

Dim showParameters As Type() = {GetType(String)}
Dim simpleShow As MethodInfo = _
    GetType(MessageBox).GetMethod("Show", showParameters)

ilgen.Emit(OpCodes.Ldstr, _
    "This event handler was constructed at run time.")
ilgen.Emit(OpCodes.Call, simpleShow)
ilgen.Emit(OpCodes.Pop)
ilgen.Emit(OpCodes.Ret)

Conclua o método dinâmico chamando seu método CreateDelegate. Use o acessador add para adicionar o delegado à lista de invocação para o evento.

Delegate^ dEmitted = handler->CreateDelegate(tDelegate);
addHandler->Invoke(exFormAsObj, gcnew array<Object^> { dEmitted });

Delegate dEmitted = handler.CreateDelegate(tDelegate);
addHandler.Invoke(exFormAsObj, new Object[] { dEmitted });

Dim dEmitted As [Delegate] = handler.CreateDelegate(tDelegate)
miAddHandler.Invoke(exFormAsObj, New Object() {dEmitted})

Teste o evento. O código a seguir carrega o formulário definido no exemplo de código. Clicar no formulário invoca o manipulador de eventos predefinido e o manipulador de eventos emitido.
```
Application::Run((Form^) exFormAsObj);
```
```
Application.Run((Form) exFormAsObj);
```
```
Application.Run(CType(exFormAsObj, Form))
```

Exemplo

O exemplo de código a seguir mostra como conectar um método existente a um evento usando a reflexão e também como usar a classe DynamicMethod para emitir um método em tempo de execução e conectá-lo a um evento.

#using <System.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::Reflection;
using namespace System::Reflection::Emit;
using namespace System::Windows::Forms;

public ref class ExampleForm : public Form
{
public:
    ExampleForm() : Form()
    {
        this->Text = "Click me";
    }
};

public ref class Example
{
public:
    static void Main()
    {
        Example^ ex = gcnew Example();
        ex->HookUpDelegate();
    }

private:
    void HookUpDelegate()
    {
        // Load an assembly, for example using the Assembly.Load
        // method. In this case, the executing assembly is loaded, to
        // keep the demonstration simple.
        //
        Assembly^ assem = Example::typeid->Assembly;

        // Get the type that is to be loaded, and create an instance
        // of it. Activator::CreateInstance has other overloads, if
        // the type lacks a default constructor. The new instance
        // is stored as type Object, to maintain the fiction that
        // nothing is known about the assembly. (Note that you can
        // get the types in an assembly without knowing their names
        // in advance.)
        //
        Type^ tExForm = assem->GetType("ExampleForm");
        Object^ exFormAsObj = Activator::CreateInstance(tExForm);

        // Get an EventInfo representing the Click event, and get the
        // type of delegate that handles the event.
        //
        EventInfo^ evClick = tExForm->GetEvent("Click");
        Type^ tDelegate = evClick->EventHandlerType;

        // If you already have a method with the correct signature,
        // you can simply get a MethodInfo for it. 
        //
        MethodInfo^ miHandler =
            Type::GetType("Example")->GetMethod("LuckyHandler",
                BindingFlags::NonPublic | BindingFlags::Instance);
            
        // Create an instance of the delegate. Using the overloads
        // of CreateDelegate that take MethodInfo is recommended.
        //
        Delegate^ d = Delegate::CreateDelegate(tDelegate, this, miHandler);

        // Get the "add" accessor of the event and invoke it late-
        // bound, passing in the delegate instance. This is equivalent
        // to using the += operator in C#, or AddHandler in Visual
        // Basic. The instance on which the "add" accessor is invoked
        // is the form; the arguments must be passed as an array.
        //
        MethodInfo^ addHandler = evClick->GetAddMethod();
        array<Object^>^ addHandlerArgs = { d };
        addHandler->Invoke(exFormAsObj, addHandlerArgs);

        // Event handler methods can also be generated at run time,
        // using lightweight dynamic methods and Reflection.Emit.
        // To construct an event handler, you need the return type
        // and parameter types of the delegate. These can be obtained
        // by examining the delegate's Invoke method. 
        //
        // It is not necessary to name dynamic methods, so the empty 
        // string can be used. The last argument associates the 
        // dynamic method with the current type, giving the delegate
        // access to all the public and private members of Example,
        // as if it were an instance method.
        //
        Type^ returnType = GetDelegateReturnType(tDelegate);
        if (returnType != void::typeid)
            throw gcnew ApplicationException("Delegate has a return type.");
            
        DynamicMethod^ handler =
            gcnew DynamicMethod("",
                              nullptr,
                              GetDelegateParameterTypes(tDelegate),
                              Example::typeid);

        // Generate a method body. This method loads a string, calls 
        // the Show method overload that takes a string, pops the
        // return value off the stack (because the handler has no
        // return type), and returns.
        //
        ILGenerator^ ilgen = handler->GetILGenerator();

        array<Type^>^ showParameters = { String::typeid };
        MethodInfo^ simpleShow =
            MessageBox::typeid->GetMethod("Show", showParameters);

        ilgen->Emit(OpCodes::Ldstr,
            "This event handler was constructed at run time.");
        ilgen->Emit(OpCodes::Call, simpleShow);
        ilgen->Emit(OpCodes::Pop);
        ilgen->Emit(OpCodes::Ret);

        // Complete the dynamic method by calling its CreateDelegate
        // method. Use the "add" accessor to add the delegate to
        // the invocation list for the event.
        //
        Delegate^ dEmitted = handler->CreateDelegate(tDelegate);
        addHandler->Invoke(exFormAsObj, gcnew array<Object^> { dEmitted });

        // Show the form. Clicking on the form causes the two
        // delegates to be invoked.
        //
        Application::Run((Form^) exFormAsObj);
    }

    void LuckyHandler(Object^ sender, EventArgs^ e)
    {
        MessageBox::Show("This event handler just happened to be lying around.");
    }

    array<Type^>^ GetDelegateParameterTypes(Type^ d)
    {
        if (d->BaseType != MulticastDelegate::typeid)
            throw gcnew ApplicationException("Not a delegate.");

        MethodInfo^ invoke = d->GetMethod("Invoke");
        if (invoke == nullptr)
            throw gcnew ApplicationException("Not a delegate.");

        array<ParameterInfo^>^ parameters = invoke->GetParameters();
        array<Type^>^ typeParameters = gcnew array<Type^>(parameters->Length);
        for (int i = 0; i < parameters->Length; i++)
        {
            typeParameters[i] = parameters[i]->ParameterType;
        }
        return typeParameters;
    }

    Type^ GetDelegateReturnType(Type^ d)
    {
        if (d->BaseType != MulticastDelegate::typeid)
            throw gcnew ApplicationException("Not a delegate.");

        MethodInfo^ invoke = d->GetMethod("Invoke");
        if (invoke == nullptr)
            throw gcnew ApplicationException("Not a delegate.");

        return invoke->ReturnType;
    }
};

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

using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Windows.Forms;

class ExampleForm : Form
{
    public ExampleForm() : base()
    {
        this.Text = "Click me";
    }
}

class Example
{
    public static void Main()
    {
        Example ex = new Example();
        ex.HookUpDelegate();
    }

    private void HookUpDelegate()
    {
        // Load an assembly, for example using the Assembly.Load
        // method. In this case, the executing assembly is loaded, to
        // keep the demonstration simple.
        //
        Assembly assem = typeof(Example).Assembly;

        // Get the type that is to be loaded, and create an instance
        // of it. Activator.CreateInstance has other overloads, if
        // the type lacks a default constructor. The new instance
        // is stored as type Object, to maintain the fiction that
        // nothing is known about the assembly. (Note that you can
        // get the types in an assembly without knowing their names
        // in advance.)
        //
        Type tExForm = assem.GetType("ExampleForm");
        Object exFormAsObj = Activator.CreateInstance(tExForm);

        // Get an EventInfo representing the Click event, and get the
        // type of delegate that handles the event.
        //
        EventInfo evClick = tExForm.GetEvent("Click");
        Type tDelegate = evClick.EventHandlerType;

        // If you already have a method with the correct signature,
        // you can simply get a MethodInfo for it.
        //
        MethodInfo miHandler =
            typeof(Example).GetMethod("LuckyHandler",
                BindingFlags.NonPublic | BindingFlags.Instance);
            
        // Create an instance of the delegate. Using the overloads
        // of CreateDelegate that take MethodInfo is recommended.
        //
        Delegate d = Delegate.CreateDelegate(tDelegate, this, miHandler);

        // Get the "add" accessor of the event and invoke it late-
        // bound, passing in the delegate instance. This is equivalent
        // to using the += operator in C#, or AddHandler in Visual
        // Basic. The instance on which the "add" accessor is invoked
        // is the form; the arguments must be passed as an array.
        //
        MethodInfo addHandler = evClick.GetAddMethod();
        Object[] addHandlerArgs = { d };
        addHandler.Invoke(exFormAsObj, addHandlerArgs);

        // Event handler methods can also be generated at run time,
        // using lightweight dynamic methods and Reflection.Emit.
        // To construct an event handler, you need the return type
        // and parameter types of the delegate. These can be obtained
        // by examining the delegate's Invoke method.
        //
        // It is not necessary to name dynamic methods, so the empty
        // string can be used. The last argument associates the
        // dynamic method with the current type, giving the delegate
        // access to all the public and private members of Example,
        // as if it were an instance method.
        //
        Type returnType = GetDelegateReturnType(tDelegate);
        if (returnType != typeof(void))
            throw new ArgumentException("Delegate has a return type.", nameof(d));

        DynamicMethod handler =
            new DynamicMethod("",
                              null,
                              GetDelegateParameterTypes(tDelegate),
                              typeof(Example));

        // Generate a method body. This method loads a string, calls
        // the Show method overload that takes a string, pops the
        // return value off the stack (because the handler has no
        // return type), and returns.
        //
        ILGenerator ilgen = handler.GetILGenerator();

        Type[] showParameters = { typeof(String) };
        MethodInfo simpleShow =
            typeof(MessageBox).GetMethod("Show", showParameters);

        ilgen.Emit(OpCodes.Ldstr,
            "This event handler was constructed at run time.");
        ilgen.Emit(OpCodes.Call, simpleShow);
        ilgen.Emit(OpCodes.Pop);
        ilgen.Emit(OpCodes.Ret);

        // Complete the dynamic method by calling its CreateDelegate
        // method. Use the "add" accessor to add the delegate to
        // the invocation list for the event.
        //
        Delegate dEmitted = handler.CreateDelegate(tDelegate);
        addHandler.Invoke(exFormAsObj, new Object[] { dEmitted });

        // Show the form. Clicking on the form causes the two
        // delegates to be invoked.
        //
        Application.Run((Form) exFormAsObj);
    }

    private void LuckyHandler(Object sender, EventArgs e)
    {
        MessageBox.Show("This event handler just happened to be lying around.");
    }

    private Type[] GetDelegateParameterTypes(Type d)
    {
        if (d.BaseType != typeof(MulticastDelegate))
            throw new ArgumentException("Not a delegate.", nameof(d));

        MethodInfo invoke = d.GetMethod("Invoke");
        if (invoke == null)
            throw new ArgumentException("Not a delegate.", nameof(d));

        ParameterInfo[] parameters = invoke.GetParameters();
        Type[] typeParameters = new Type[parameters.Length];
        for (int i = 0; i < parameters.Length; i++)
        {
            typeParameters[i] = parameters[i].ParameterType;
        }
        return typeParameters;
    }

    private Type GetDelegateReturnType(Type d)
    {
        if (d.BaseType != typeof(MulticastDelegate))
            throw new ArgumentException("Not a delegate.", nameof(d));

        MethodInfo invoke = d.GetMethod("Invoke");
        if (invoke == null)
            throw new ArgumentException("Not a delegate.", nameof(d));

        return invoke.ReturnType;
    }
}

Imports System.Reflection
Imports System.Reflection.Emit
Imports System.Windows.Forms

Class ExampleForm
    Inherits Form

    Public Sub New()
        Me.Text = "Click me"

    End Sub
End Class

Class Example
    Public Shared Sub Main()
        Dim ex As New Example()
        ex.HookUpDelegate()
    End Sub

    Private Sub HookUpDelegate()
        ' Load an assembly, for example using the Assembly.Load
        ' method. In this case, the executing assembly is loaded, to
        ' keep the demonstration simple.
        '
        Dim assem As Assembly = GetType(Example).Assembly

        ' Get the type that is to be loaded, and create an instance 
        ' of it. Activator.CreateInstance also has an overload that
        ' takes an array of types representing the types of the 
        ' constructor parameters, if the type you are creating does
        ' not have a parameterless constructor. The new instance
        ' is stored as type Object, to maintain the fiction that 
        ' nothing is known about the assembly. (Note that you can
        ' get the types in an assembly without knowing their names
        ' in advance.)
        '
        Dim tExForm As Type = assem.GetType("ExampleForm")
        Dim exFormAsObj As Object = _
            Activator.CreateInstance(tExForm)

        ' Get an EventInfo representing the Click event, and get the
        ' type of delegate that handles the event.
        '
        Dim evClick As EventInfo = tExForm.GetEvent("Click")
        Dim tDelegate As Type = evClick.EventHandlerType

        ' If you already have a method with the correct signature,
        ' you can simply get a MethodInfo for it. 
        '
        Dim miHandler As MethodInfo = _
            GetType(Example).GetMethod("LuckyHandler", _
                BindingFlags.NonPublic Or BindingFlags.Instance)
        ' Create an instance of the delegate. Using the overloads
        ' of CreateDelegate that take MethodInfo is recommended.
        '
        Dim d As [Delegate] = _
            [Delegate].CreateDelegate(tDelegate, Me, miHandler)

        ' Get the "add" accessor of the event and invoke it late-
        ' bound, passing in the delegate instance. This is equivalent
        ' to using the += operator in C#, or AddHandler in Visual
        ' Basic. The instance on which the "add" accessor is invoked
        ' is the form; the arguments must be passed as an array.
        '
        Dim miAddHandler As MethodInfo = evClick.GetAddMethod()
        Dim addHandlerArgs() As Object = {d}
        miAddHandler.Invoke(exFormAsObj, addHandlerArgs)

        ' Event handler methods can also be generated at run time,
        ' using lightweight dynamic methods and Reflection.Emit. 
        ' To construct an event handler, you need the return type
        ' and parameter types of the delegate. These can be obtained
        ' by examining the delegate's Invoke method. 
        '
        ' It is not necessary to name dynamic methods, so the empty 
        ' string can be used. The last argument associates the 
        ' dynamic method with the current type, giving the delegate
        ' access to all the public and private members of Example,
        ' as if it were an instance method.
        '
        Dim returnType As Type = GetDelegateReturnType(tDelegate)
        If returnType IsNot GetType(Void) Then
            Throw New ArgumentException("Delegate has a return type.", NameOf(d))
        End If

        Dim handler As New DynamicMethod( _
            "", _
            Nothing, _
            GetDelegateParameterTypes(tDelegate), _
            GetType(Example) _
        )

        ' Generate a method body. This method loads a string, calls 
        ' the Show method overload that takes a string, pops the 
        ' return value off the stack (because the handler has no
        ' return type), and returns.
        '
        Dim ilgen As ILGenerator = handler.GetILGenerator()

        Dim showParameters As Type() = {GetType(String)}
        Dim simpleShow As MethodInfo = _
            GetType(MessageBox).GetMethod("Show", showParameters)

        ilgen.Emit(OpCodes.Ldstr, _
            "This event handler was constructed at run time.")
        ilgen.Emit(OpCodes.Call, simpleShow)
        ilgen.Emit(OpCodes.Pop)
        ilgen.Emit(OpCodes.Ret)

        ' Complete the dynamic method by calling its CreateDelegate
        ' method. Use the "add" accessor to add the delegate to
        ' the invocation list for the event.
        '
        Dim dEmitted As [Delegate] = handler.CreateDelegate(tDelegate)
        miAddHandler.Invoke(exFormAsObj, New Object() {dEmitted})

        ' Show the form. Clicking on the form causes the two
        ' delegates to be invoked.
        '
        Application.Run(CType(exFormAsObj, Form))

    End Sub

    Private Sub LuckyHandler(ByVal sender As [Object], _
        ByVal e As EventArgs)

        MessageBox.Show("This event handler just happened to be lying around.")
    End Sub

    Private Function GetDelegateParameterTypes(ByVal d As Type) _
        As Type()

        If d.BaseType IsNot GetType(MulticastDelegate) Then
            Throw New ArgumentException("Not a delegate.", NameOf(d))
        End If

        Dim invoke As MethodInfo = d.GetMethod("Invoke")
        If invoke Is Nothing Then
            Throw New ArgumentException("Not a delegate.", NameOf(d))
        End If

        Dim parameters As ParameterInfo() = invoke.GetParameters()
        ' Dimension this array Length - 1, because VB adds an extra
        ' element to zero-based arrays.
        Dim typeParameters(parameters.Length - 1) As Type
        For i As Integer = 0 To parameters.Length - 1
            typeParameters(i) = parameters(i).ParameterType
        Next i

        Return typeParameters

    End Function


    Private Function GetDelegateReturnType(ByVal d As Type) As Type

        If d.BaseType IsNot GetType(MulticastDelegate) Then
            Throw New ArgumentException("Not a delegate.", NameOf(d))
        End If

        Dim invoke As MethodInfo = d.GetMethod("Invoke")
        If invoke Is Nothing Then
            Throw New ArgumentException("Not a delegate.", NameOf(d))
        End If

        Return invoke.ReturnType

    End Function
End Class

Como conectar um delegado usando a reflexão

Para conectar um delegado usando reflexão

Gerar um manipulador de eventos em tempo de execução usando um método dinâmico

Exemplo

Confira também

Comentários

Recursos adicionais