private void AttachEventHandler(EventInfo eventInfo, Func <DateTime> utcNow)
{
if (!recorderMap.TryGetValue(eventInfo.Name, out _))
{
var recorder = new EventRecorder(subject.Target, eventInfo.Name, utcNow);
if (recorderMap.TryAdd(eventInfo.Name, recorder))
{
recorder.Attach(subject, eventInfo);
}
}
}
/// <summary>
/// Obtains the <see cref="EventRecorder"/> for a particular event of the <paramref name="eventSource"/>.
/// </summary>
/// <param name="eventSource">The object for which to get an event recorder.</param>
/// <param name="eventName">The name of the event.</param>
/// <returns></returns>
public static EventRecorder GetRecorderForEvent <T>(this T eventSource, string eventName)
{
EventRecorder eventRecorder = Map[eventSource].FirstOrDefault(r => r.EventName == eventName);
if (eventRecorder == null)
{
string name = eventSource.GetType().Name;
throw new InvalidOperationException(String.Format(
"Type <{0}> does not expose an event named \"{1}\".", name, eventName));
}
return(eventRecorder);
}
public void DeletingACounterShouldRaiseTheCollectionChangedEvent()
{
var dbfile = Path.Combine(RootPath, Guid.NewGuid().ToString("N") + ".db3");
DatabaseHelper.CreateDatabase(dbfile);
var db = new DatabaseHelper();
var counter = new Counter
{
Name = "TestCounter",
Description = "A test counter"
};
var res = Task.Run(async () =>
{
await db.AddOrUpdateCounterAsync(counter);
return 0;
}).Result;
var eventRecorder = new EventRecorder(db, nameof(DatabaseHelper.CountersChanged));
eventRecorder.RecordEvent();
res = Task.Run(async () =>
{
await db.DeleteCounterAsync(counter);
return 0;
}).Result;
eventRecorder.Should().HaveCount(1);
}
/// <summary>
/// Generates an eventhandler for an event of type eventSignature that calls RegisterEvent on recorder
/// when invoked.
/// </summary>
public static Delegate GenerateHandler(Type eventSignature, EventRecorder recorder)
{
Type returnType = GetDelegateReturnType(eventSignature);
Type[] parameters = GetDelegateParameterTypes(eventSignature);
Module module = recorder.GetType()
.Module;
var eventHandler = new DynamicMethod(
eventSignature.Name + "DynamicHandler",
returnType,
AppendParameterListThisReference(parameters),
module);
MethodInfo methodToCall = typeof(EventRecorder).GetMethod(nameof(EventRecorder.RecordEvent),
BindingFlags.Instance | BindingFlags.Public);
ILGenerator ilGen = eventHandler.GetILGenerator();
// Make room for the one and only local variable in our function
ilGen.DeclareLocal(typeof(object[]));
// Create the object array for the parameters and store in local var index 0
ilGen.Emit(OpCodes.Ldc_I4, parameters.Length);
ilGen.Emit(OpCodes.Newarr, typeof(object));
ilGen.Emit(OpCodes.Stloc_0);
for (var index = 0; index < parameters.Length; index++)
{
// Push the object array onto the evaluation stack
ilGen.Emit(OpCodes.Ldloc_0);
// Push the array index to store our parameter in onto the evaluation stack
ilGen.Emit(OpCodes.Ldc_I4, index);
// Load the parameter
ilGen.Emit(OpCodes.Ldarg, index + 1);
// Box value-type parameters
if (parameters[index].IsValueType)
{
ilGen.Emit(OpCodes.Box, parameters[index]);
}
// Store the parameter in the object array
ilGen.Emit(OpCodes.Stelem_Ref);
}
// Push the this-reference on the stack as param 0 for calling the handler
ilGen.Emit(OpCodes.Ldarg_0);
// Push the object array onto the stack as param 1 for calling the handler
ilGen.Emit(OpCodes.Ldloc_0);
// Call the handler
ilGen.EmitCall(OpCodes.Callvirt, methodToCall, null);
ilGen.Emit(OpCodes.Ret);
return(eventHandler.CreateDelegate(eventSignature, recorder));
}
