CreateProvider(Control control, string eventName)
{
//
// Dynamically create inherited class that is strongly typed
// for the event handler.
//
EventInfo ei = control.GetType().GetEvent(eventName);
EventBroadcastProvider broadcastProvider = CreateHandlerForEvent(ei);
broadcastProvider.Bind(control, eventName);
return(broadcastProvider);
}
/// <summary>
/// Returns a derived instance of <see cref="EventBroadcastProvider"/> that
/// matches the types required by the targeted event handler.
/// </summary>
/// <param name="ei"></param>
/// <returns></returns>
private static EventBroadcastProvider CreateHandlerForEvent(EventInfo ei)
{
EventBroadcastProvider result = null;
string namespaceName = typeof(EventBroadcastProvider).Namespace;
string eventName = ei.Name;
string className = eventName + "BroadcastProvider";
AssemblyName assemblyName = new AssemblyName();
assemblyName.Name = className + "Assembly";
AppDomain appDomain = AppDomain.CurrentDomain;
AssemblyBuilder assBuilder =
appDomain.DefineDynamicAssembly(assemblyName,
AssemblyBuilderAccess.Run);
ModuleBuilder modBuilder =
assBuilder.DefineDynamicModule(className + "Module");
TypeBuilder typBuilder =
modBuilder.DefineType(className,
TypeAttributes.Public,
typeof(EventBroadcastProvider));
FieldBuilder fldBuilder =
typBuilder.DefineField("m_handler",
typeof(Delegate),
FieldAttributes.Private);
ILGenerator ilGen = null;
//
// Build the RelayDelegate property.
//
PropertyBuilder relayDelegateBuilder =
typBuilder.DefineProperty("RelayDelegate",
PropertyAttributes.None,
typeof(Delegate), null);
MethodBuilder get_relayDelegateBuilder =
typBuilder.DefineMethod("get_RelayDelegate",
MethodAttributes.HideBySig |
MethodAttributes.Virtual |
MethodAttributes.Family |
MethodAttributes.SpecialName,
typeof(Delegate), null);
ilGen = get_relayDelegateBuilder.GetILGenerator();
ilGen.DeclareLocal(typeof(Delegate));
ilGen.Emit(OpCodes.Nop);
ilGen.Emit(OpCodes.Ldarg_0);
ilGen.Emit(OpCodes.Ldfld, fldBuilder);
ilGen.Emit(OpCodes.Stloc_0);
ilGen.Emit(OpCodes.Ldloc_0);
ilGen.Emit(OpCodes.Ret);
relayDelegateBuilder.SetGetMethod(get_relayDelegateBuilder);
//
// Build the HandleEvent method.
//
MethodBuilder handleEventBuilder =
typBuilder.DefineMethod("HandleEvent",
MethodAttributes.Private | MethodAttributes.HideBySig,
null,
new Type[] { typeof(object),
ei.EventHandlerType.GetMethod("Invoke").GetParameters()[1].ParameterType });
ilGen = handleEventBuilder.GetILGenerator();
ilGen.Emit(OpCodes.Nop);
ilGen.Emit(OpCodes.Ldarg_0);
ilGen.Emit(OpCodes.Ldarg_1);
ilGen.Emit(OpCodes.Ldarg_2);
ilGen.Emit(OpCodes.Call,
typeof(EventBroadcastProvider).GetMethod("Relay",
BindingFlags.Instance | BindingFlags.NonPublic));
ilGen.Emit(OpCodes.Nop);
ilGen.Emit(OpCodes.Ret);
//
// Build the constructor.
//
ConstructorBuilder ctorBuilder =
typBuilder.DefineConstructor(MethodAttributes.Public |
MethodAttributes.HideBySig,
CallingConventions.HasThis, null);
ilGen = ctorBuilder.GetILGenerator();
ilGen.Emit(OpCodes.Ldarg_0);
ilGen.Emit(OpCodes.Ldnull);
ilGen.Emit(OpCodes.Stfld, fldBuilder);
ilGen.Emit(OpCodes.Ldarg_0);
ilGen.Emit(OpCodes.Call,
typeof(EventBroadcastProvider).
GetConstructor(BindingFlags.Instance |
BindingFlags.NonPublic, null,
Type.EmptyTypes, null));
ilGen.Emit(OpCodes.Nop);
ilGen.Emit(OpCodes.Nop);
ilGen.Emit(OpCodes.Ldarg_0);
ilGen.Emit(OpCodes.Ldarg_0);
ilGen.Emit(OpCodes.Ldftn, handleEventBuilder);
ilGen.Emit(OpCodes.Newobj, ei.EventHandlerType.GetConstructors()[0]);
ilGen.Emit(OpCodes.Stfld, fldBuilder);
ilGen.Emit(OpCodes.Nop);
ilGen.Emit(OpCodes.Ret);
result =
(EventBroadcastProvider)Activator.
CreateInstance(typBuilder.CreateType());
return(result);
}
