Вы можете скомпилировать деревья выражений для использования методов void без каких-либо аргументов в качестве обработчиков событий для событий любого типа. Чтобы приспособить другие типы обработчиков событий, вы должны каким-то образом сопоставить параметры обработчика событий с событиями.
using System;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
class ExampleEventArgs : EventArgs
{
public int IntArg {get; set;}
}
class EventRaiser
{
public event EventHandler SomethingHappened;
public event EventHandler<ExampleEventArgs> SomethingHappenedWithArg;
public void RaiseEvents()
{
if (SomethingHappened!=null) SomethingHappened(this, EventArgs.Empty);
if (SomethingHappenedWithArg!=null)
{
SomethingHappenedWithArg(this, new ExampleEventArgs{IntArg = 5});
}
}
}
class Handler
{
public void HandleEvent() { Console.WriteLine("Handler.HandleEvent() called.");}
public void HandleEventWithArg(int arg) { Console.WriteLine("Arg: {0}",arg); }
}
static class EventProxy
{
//void delegates with no parameters
static public Delegate Create(EventInfo evt, Action d)
{
var handlerType = evt.EventHandlerType;
var eventParams = handlerType.GetMethod("Invoke").GetParameters();
//lambda: (object x0, EventArgs x1) => d()
var parameters = eventParams.Select(p=>Expression.Parameter(p.ParameterType,"x"));
var body = Expression.Call(Expression.Constant(d),d.GetType().GetMethod("Invoke"));
var lambda = Expression.Lambda(body,parameters.ToArray());
return Delegate.CreateDelegate(handlerType, lambda.Compile(), "Invoke", false);
}
//void delegate with one parameter
static public Delegate Create<T>(EventInfo evt, Action<T> d)
{
var handlerType = evt.EventHandlerType;
var eventParams = handlerType.GetMethod("Invoke").GetParameters();
//lambda: (object x0, ExampleEventArgs x1) => d(x1.IntArg)
var parameters = eventParams.Select(p=>Expression.Parameter(p.ParameterType,"x")).ToArray();
var arg = getArgExpression(parameters[1], typeof(T));
var body = Expression.Call(Expression.Constant(d),d.GetType().GetMethod("Invoke"), arg);
var lambda = Expression.Lambda(body,parameters);
return Delegate.CreateDelegate(handlerType, lambda.Compile(), "Invoke", false);
}
//returns an expression that represents an argument to be passed to the delegate
static Expression getArgExpression(ParameterExpression eventArgs, Type handlerArgType)
{
if (eventArgs.Type==typeof(ExampleEventArgs) && handlerArgType==typeof(int))
{
//"x1.IntArg"
var memberInfo = eventArgs.Type.GetMember("IntArg")[0];
return Expression.MakeMemberAccess(eventArgs,memberInfo);
}
throw new NotSupportedException(eventArgs+"->"+handlerArgType);
}
}
static class Test
{
public static void Main()
{
var raiser = new EventRaiser();
var handler = new Handler();
//void delegate with no parameters
string eventName = "SomethingHappened";
var eventinfo = raiser.GetType().GetEvent(eventName);
eventinfo.AddEventHandler(raiser,EventProxy.Create(eventinfo,handler.HandleEvent));
//void delegate with one parameter
string eventName2 = "SomethingHappenedWithArg";
var eventInfo2 = raiser.GetType().GetEvent(eventName2);
eventInfo2.AddEventHandler(raiser,EventProxy.Create<int>(eventInfo2,handler.HandleEventWithArg));
//or even just:
eventinfo.AddEventHandler(raiser,EventProxy.Create(eventinfo,()=>Console.WriteLine("!")));
eventInfo2.AddEventHandler(raiser,EventProxy.Create<int>(eventInfo2,i=>Console.WriteLine(i+"!")));
raiser.RaiseEvents();
}
}