/// <summary>
/// 关闭或后退之前，返回false表示禁止关闭
/// </summary>
/// <returns>true 表允许关闭</returns>
internal async Task <bool> AllowClose()
{
if (Closing != null)
{
var args = new AsyncCancelEventArgs();
Closing(this, args);
await args.EnsureAllCompleted();
if (args.Cancel)
{
return(false);
}
}
return(await OnClosing());
}
public Deferral(AsyncCancelEventArgs p_owner)
{
_owner = p_owner;
_taskSrc = new TaskCompletionSource <bool>();
_owner.AddTask(_taskSrc.Task);
}
