EventInfo.AddEventHandler(Object, Delegate) Yöntem

public:
 virtual void AddEventHandler(System::Object ^ target, Delegate ^ handler);

public virtual void AddEventHandler (object target, Delegate handler);

public virtual void AddEventHandler (object? target, Delegate? handler);

public void AddEventHandler (object target, Delegate handler);

abstract member AddEventHandler : obj * Delegate -> unit
override this.AddEventHandler : obj * Delegate -> unit

Public Overridable Sub AddEventHandler (target As Object, handler As Delegate)

Public Sub AddEventHandler (target As Object, handler As Delegate)

Parametreler

Uygulamalar

Özel durumlar

Örnekler

Aşağıdaki örnek sınıfının bir örneğini System.Timers.Timer oluşturur, dinamik bir derleme kullanarak bir olay işleyicisi oluşturur ve dinamik olay işleyicisini bağlar. Tüm eylemler geç bağlama kullanılarak gerçekleştirilir.

Örnek Timer türünde Objectbir değişkende depolanır ve öğesine erişen Timer tüm kod bu kadar geç bağlanır. Örnek, olayı almak Elapsed için yöntemini ve EventHandlerType olayın temsilci türünü almak için özelliğini kullanırType.GetEvent.

Örnek, temsilci türünün yöntemi için Invoke bir MethodInfo alır ve örnekten temsilcinin imzasını MethodInfo alır. Örnek daha sonra adlı Handler tek bir türü içeren bir modül ile dinamik bir derleme oluşturur ve türüne olayı işleyen adlı DynamicHandler bir static yöntem (SharedVisual Basic'te yöntem) verir.

Dinamik tür oluşturulduktan sonra, örnek tamamlanmış yöntem için bir MethodInfo alır ve bunu kullanarak bir temsilci örneği oluşturur. Bu örnek, olayı bağlamak için yöntemine geçirilir AddEventHandler . Ardından program, olayın tetiklenebilmesi için duraklatılır.

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

public class Example
{
    private static object? timer;

    public static void Main()
    {
        // Get the Timer type.
        Type t = typeof(System.Timers.Timer);
        // Create an instance of the Timer type.
        timer = Activator.CreateInstance(t);

        // Use reflection to get the Elapsed event.
        EventInfo? eInfo = t.GetEvent("Elapsed");

        // In order to create a method to handle the Elapsed event,
        // it is necessary to know the signature of the delegate
        // used to raise the event. Reflection.Emit can then be
        // used to construct a dynamic class with a static method
        // that has the correct signature.

        // Get the event handler type of the Elapsed event. This is
        // a delegate type, so it has an Invoke method that has
        // the same signature as the delegate. The following code
        // creates an array of Type objects that represent the
        // parameter types of the Invoke method.
        //
        Type? handlerType = eInfo?.EventHandlerType;
        MethodInfo? invokeMethod = handlerType?.GetMethod("Invoke");
        ParameterInfo[]? parms = invokeMethod?.GetParameters();
        Type[] parmTypes = new Type[parms?.Length ?? 0];
        for (int i = 0; i < parms?.Length; i++)
        {
            parmTypes[i] = parms[i].ParameterType;
        }

        // Use Reflection.Emit to create a dynamic assembly that
        // will be run but not saved. An assembly must have at
        // least one module, which in this case contains a single
        // type. The only purpose of this type is to contain the
        // event handler method. (You can use also dynamic methods,
        // which are simpler because there is no need to create an
        // assembly, module, or type.)
        //
        AssemblyName aName = new AssemblyName();
        aName.Name = "DynamicTypes";
        AssemblyBuilder ab = AssemblyBuilder.DefineDynamicAssembly(aName, AssemblyBuilderAccess.Run);
        ModuleBuilder mb = ab.DefineDynamicModule(aName.Name);
        TypeBuilder tb = mb.DefineType("Handler", TypeAttributes.Class | TypeAttributes.Public);

        // Create the method that will handle the event. The name
        // is not important. The method is static, because there is
        // no reason to create an instance of the dynamic type.
        //
        // The parameter types and return type of the method are
        // the same as those of the delegate's Invoke method,
        // captured earlier.
        MethodBuilder handler = tb.DefineMethod("DynamicHandler",
            MethodAttributes.Public | MethodAttributes.Static,
            invokeMethod?.ReturnType, parmTypes);

        // Generate code to handle the event. In this case, the
        // handler simply prints a text string to the console.
        //
        ILGenerator il = handler.GetILGenerator();
        il.EmitWriteLine("Timer's Elapsed event is raised.");
        il.Emit(OpCodes.Ret);

        // CreateType must be called before the Handler type can
        // be used. In order to create the delegate that will
        // handle the event, a MethodInfo from the finished type
        // is required.
        Type? finished = tb.CreateType();
        MethodInfo? eventHandler = finished?.GetMethod("DynamicHandler");

        // Use the MethodInfo to create a delegate of the correct
        // type, and call the AddEventHandler method to hook up
        // the event.
        if (handlerType is not null && eventHandler is not null)
        {
            Delegate d = Delegate.CreateDelegate(handlerType, eventHandler);
            eInfo?.AddEventHandler(timer, d);
        }

        // Late-bound calls to the Interval and Enabled property
        // are required to enable the timer with a one-second
        // interval.
        t.InvokeMember("Interval", BindingFlags.SetProperty, null, timer, new Object[] { 1000 });
        t.InvokeMember("Enabled", BindingFlags.SetProperty, null, timer, new Object[] { true });

        Console.WriteLine("Press the Enter key to end the program.");
        Console.ReadLine();
    }
}
/* This example produces output similar to the following:

Press the Enter key to end the program.
Timer's Elapsed event is raised.
Timer's Elapsed event is raised.
Timer's Elapsed event is raised.
*/

Imports System.Reflection
Imports System.Reflection.Emit

Public Class Example

    Private Shared timer As Object
    
    Public Shared Sub Main() 
        ' Get the Timer type.
        Dim t As Type = GetType(System.Timers.Timer)
        ' Create an instance of the Timer type.
        timer = Activator.CreateInstance(t)
        
        ' Use reflection to get the Elapsed event.
        Dim eInfo As EventInfo = t.GetEvent("Elapsed")
        
        ' In order to create a method to handle the Elapsed event,
        ' it is necessary to know the signature of the delegate 
        ' used to raise the event. Reflection.Emit can then be
        ' used to construct a dynamic class with a static method
        ' that has the correct signature.
        '
        ' Get the event handler type of the Elapsed event. This is
        ' a delegate type, so it has an Invoke method that has
        ' the same signature as the delegate. The following code
        ' creates an array of Type objects that represent the 
        ' parameter types of the Invoke method.
        '
        Dim handlerType As Type = eInfo.EventHandlerType
        Dim invokeMethod As MethodInfo = handlerType.GetMethod("Invoke")
        Dim parms As ParameterInfo() = invokeMethod.GetParameters()
        '
        ' Note that in Visual Basic you must dimension the array one
        ' unit smaller than the source array in order to get an array
        ' of the same size. This is because Visual Basic adds an extra
        ' element to every array, for ease of use.
        '
        Dim parmTypes(parms.Length - 1) As Type
        Dim i As Integer
        For i = 0 To parms.Length - 1
            parmTypes(i) = parms(i).ParameterType
        Next i
        
        ' Use Reflection.Emit to create a dynamic assembly that
        ' will be run but not saved. An assembly must have at 
        ' least one module, which in this case contains a single
        ' type. The only purpose of this type is to contain the 
        ' event handler method. (You can alsso use dynamic methods, 
        ' which are simpler because there is no need to create an 
        ' assembly, module, or type.)
        Dim aName As New AssemblyName()
        aName.Name = "DynamicTypes"
        Dim ab As AssemblyBuilder = AssemblyBuilder.DefineDynamicAssembly(aName, AssemblyBuilderAccess.Run)
        Dim mb As ModuleBuilder = ab.DefineDynamicModule(aName.Name)
        Dim tb As TypeBuilder = mb.DefineType("Handler", TypeAttributes.Class Or TypeAttributes.Public)
        
        ' Create the method that will handle the event. The name
        ' is not important. The method is Shared ("static" in 
        ' reflection), because there is no reason to create an 
        ' instance of the dynamic type "Handler".
        '
        ' The parameter types and return type of the method are
        ' the same as those of the delegate's Invoke method, 
        ' captured earlier.
        Dim handler As MethodBuilder = tb.DefineMethod("DynamicHandler", MethodAttributes.Public Or MethodAttributes.Static, invokeMethod.ReturnType, parmTypes)
        
        ' Generate code to handle the event. In this case, the 
        ' handler simply prints a text string to the console.
        '
        Dim il As ILGenerator = handler.GetILGenerator()
        il.EmitWriteLine("Timer's Elapsed event is raised.")
        il.Emit(OpCodes.Ret)
        
        ' CreateType must be called before the Handler type can
        ' be used. In order to create the delegate that will
        ' handle the event, a MethodInfo from the finished type
        ' is required.
        Dim finished As Type = tb.CreateType()
        Dim eventHandler As MethodInfo = finished.GetMethod("DynamicHandler")
        
        ' Use the MethodInfo to create a delegate of the correct 
        ' type, and call the AddEventHandler method to hook up 
        ' the event.
        Dim d As [Delegate] = [Delegate].CreateDelegate(handlerType, eventHandler)
        eInfo.AddEventHandler(timer, d)
        
        ' Late-bound calls to the Interval and Enabled property 
        ' are required to enable the timer with a one-second
        ' interval.
        t.InvokeMember("Interval", BindingFlags.SetProperty, Nothing, timer, New [Object]() {1000})
        t.InvokeMember("Enabled", BindingFlags.SetProperty, Nothing, timer, New [Object]() {True})
        
        Console.WriteLine("Press the Enter key to end the program.")
        Console.ReadLine()
    
    End Sub 
End Class 
' This example produces output similar to the following:
'      Press the Enter key to end the program.
'      Timer's Elapsed event is raised.
'      Timer's Elapsed event is raised.
'      Timer's Elapsed event is raised.

Açıklamalar

Bu yöntem, hedef nesnedeki olayı eşitlemek için bir temsilci eklemeyi dener.

Olay hedef parametresi tarafından her tetiklendiğinde, işleyici tarafından kapsüllenen yöntem veya yöntemler çağrılır.

Program zaten derlendiğinde, C# += söz dizimini veya Visual Basic WithEvents ve Handles anahtar sözcükleri kullanarak olayı bağlamak mümkün olmadığında bir tür yüklediğinizde yöntemini kullanabilirsinizAddEventHandler.

Şunlara uygulanır

Ayrıca bkz.

• Object
• Delegate
• EventHandler