C#.NET 删除事件所有订阅

            var instance = FastReport.Utils.Config.DesignerSettings; //实例
            var eventName = "CustomSaveDialog"; //需要删除所有订阅的事件名称

            //删除旧的事件，避免重复添加事件
            FieldInfo fieldInfo = instance.GetType().GetField(eventName, BindingFlags.NonPublic | BindingFlags.Instance);
            if (fieldInfo != null)
            {
                var eventDelegate = fieldInfo.GetValue(instance) as Delegate;

                if (eventDelegate != null)
                {
                    var handleList = eventDelegate.GetInvocationList();
                    foreach (Delegate handler in handleList)
                    {
                        instance.CustomSaveDialog -= (OpenSaveDialogEventHandler)handler; //删除订阅
                    }
                }
            }