/// <summary>
/// This method will try to fetch all live event handlers,
/// and invokes each handler with the arguments.
/// If a non-null <see cref="SynchronizationContext"/> has been set, it is checked
/// by each handler.
/// </summary>
/// <param name="sender">NOT tested here.</param>
/// <param name="eventArgs">NOT tested here.</param>
/// <param name="sendOrPostPolicy">Invoke selection. Defaults to
/// <see cref="SendOrPostPolicy.InvokeSafePostSafeOrInvokeUnknown"/>.</param>
/// <returns>False if NO handlers are alive and the event is NOT invoked.
/// True if the live handlers are all completed when this returns.
/// Null if any live handler is Posted to the <see cref="SynchronizationContext"/>.</returns>
public bool?TryInvoke(
object sender,
TEventArgs eventArgs,
SendOrPostPolicy sendOrPostPolicy = SendOrPostPolicy.InvokeSafePostSafeOrInvokeUnknown)
{
bool?result = false;
foreach (WeakEventDelegate <TEventArgs> weakEventDelegate in enumerateLiveDelegates())
{
switch (weakEventDelegate.TryInvoke(sender, eventArgs, sendOrPostPolicy))
{
case null:
result = null;
break;
case true:
if (result == false)
{
result = true;
}
break;
}
}
return(result);
}
/// <summary>
/// This method will try to fetch the event handler now and invoke the handler with the arguments.
/// If a non-null <see cref="SynchronizationContext"/> has been set, it is checked,
/// and this will Post, Send, or Invoke the handler, checking the current
/// <see cref="SynchronizationContext"/> and the <see cref="SendOrPostPolicy"/>.
/// </summary>
/// <param name="sender">NOT tested here.</param>
/// <param name="eventArgs">NOT tested here.</param>
/// <param name="sendOrPostPolicy">Invoke selection. Defaults to
/// <see cref="SendOrPostPolicy.InvokeSafePostSafeOrInvokeUnknown"/>.</param>
/// <returns>False if the object is NOT alive and the handler is not invoked.
/// True if the handler is completed when this returns.
/// Null if the handler is Posted to the <see cref="SynchronizationContext"/>.</returns>
public bool?TryInvoke(
object sender,
TEventArgs eventArgs,
SendOrPostPolicy sendOrPostPolicy = SendOrPostPolicy.InvokeSafePostSafeOrInvokeUnknown)
{
if (!TryGetTarget(out EventHandler <TEventArgs> eventHandler))
{
return(false);
}
Task result = SynchronizationContext.SendOrPost(
SendOrPostCallback,
(eventHandler, sender, eventArgs),
sendOrPostPolicy);
void SendOrPostCallback((EventHandler <TEventArgs> handler, object source, TEventArgs args) state)
=> OnInvokeHandler(state.handler, state.source, state.args);
return(result.IsCompleted
? true
: (bool?)null);
}
