Currently if there are several appointments with equal start date, their order in TimelineView for example cannot be defined via a custom sort comparer.

With the current WeeklyPrintStyle, when you select a StartDate it "jumps" to the previous Monday. There should be a way (another style or improvement to the current weekly style) to select a different week start day.

How to reproduce: check the attached (video radscheduler-selection-incorrect.gif)
 public RadForm1()
 {
     InitializeComponent();

     Appointment appointment = new Appointment(DateTime.Today.AddHours(13), TimeSpan.FromHours(1), "Test Appointment");
     this.radScheduler1.Appointments.Add(appointment);

     for (int i = 0; i < 25; i++)
     {
         appointment = new Appointment(DateTime.Today.AddHours(24), TimeSpan.FromHours(1), "AllDay: " + i);
         appointment.AllDay = true;
         this.radScheduler1.Appointments.Add(appointment);
     }
     this.radScheduler1.AllowAppointmentsMultiSelect = true;
 }

Workaround: create a custom input behavior

this.radScheduler1.SchedulerInputBehavior = new CustomSchedulerInputBehavior(this.radScheduler1);

public class CustomSchedulerInputBehavior : SchedulerInputBehavior
{
    public CustomSchedulerInputBehavior(RadScheduler scheduler) 
        : base(scheduler)
    {
    }

    public override bool HandleMouseWheel(MouseEventArgs args)
    {
        if (!this.Scheduler.AllowMouseWheelSupport)
            return false;

        bool scrolled = false;

        if (this.Scheduler.SelectionBehavior.IsAllDayAreaSelection || this.IsLastSelectedAppointmentAllDay(this.Scheduler.SelectionBehavior.SelectedAppointments))
        {
            if (this.Scheduler.GroupType == GroupType.Resource)
            {
                SchedulerDayViewGroupedByResourceElement grouped = this.Scheduler.ViewElement as SchedulerDayViewGroupedByResourceElement;
                IList<SchedulerDayViewElement> childViews = grouped != null ? grouped.GetChildViewElements() : null;
                if (childViews != null && childViews.Count > 0)
                {
                    RadScrollBarElement scroll = childViews[childViews.Count - 1].AllDayHeaderElement.ScrollBar;
                    if (scroll.Visibility != ElementVisibility.Collapsed)
                    {
                        int newValue = scroll.Value - childViews[childViews.Count - 1].AllDayHeaderElement.HeaderHeight * Math.Sign(args.Delta);
                        newValue = Math.Max(Math.Min(newValue, scroll.Maximum - scroll.LargeChange + 1), scroll.Minimum);
                        scroll.Value = newValue;
                        scrolled = true;
                    }
                }
            }
            else
            {
                SchedulerDayViewElement dayView = this.Scheduler.ViewElement as SchedulerDayViewElement;
                RadScrollBarElement scroll = dayView != null ? dayView.AllDayHeaderElement.ScrollBar : null;

                if (scroll != null && scroll.Visibility != ElementVisibility.Collapsed)
                {
                    int newValue = scroll.Value - dayView.AllDayHeaderElement.HeaderHeight * Math.Sign(args.Delta);
                    newValue = Math.Max(Math.Min(newValue, scroll.Maximum - scroll.LargeChange + 1), scroll.Minimum);
                    scroll.Value = newValue;
                    scrolled = true;
                }
            }
        }

        if (scrolled)
        {
            return false;
        }

        if (args.Delta > 0)
        {
            this.Scheduler.ViewElement.Scroll(true);
        }
        else
        {
            this.Scheduler.ViewElement.Scroll(false);
        }
        return false;
    }

    private bool IsLastSelectedAppointmentAllDay(ReadOnlyCollection<IEvent> selectedAppointments)
    {
        if (selectedAppointments.Count > 0)
        {
            return selectedAppointments[selectedAppointments.Count - 1].AllDay;
        }

        return false;
    }

}

To reproduce:
RadSchedulerLocalizationProvider.CurrentProvider = new CustomSchedulerLocalizationProvider();

radScheduler1.Appointments.Add(new Appointment(DateTime.Now.AddDays(-5), DateTime.Now.AddDays(-4)));
radScheduler1.Appointments.Add(new Appointment(DateTime.Now.AddDays(5), DateTime.Now.AddDays(4)));

Workaround:
radScheduler1.SchedulerElement.Refresh();

The end user should be able to resize or move recurring appointments. As a result, either an exception occurrence should be created or the whole series should be modified.

RadScheduler refreshes slow its visuals in grouped DayView when scrolling through the resources or changing the view's date.

Allow customizing the Confirm Delete dialog

Please refer to the attached screenshot from Outlook.

FIX. RadScheduler - AppointmentDeleted is fired even though the user cancelled the deletion (pressed Cancel on the dialog)

When ShowAllDayArea is false, and you add an appointment on a single day from 00:00 to 24:00, the appointment will appear twice.

When you select multiple cells in MultiDayView and right-click somewhere to open the context menu, some of the cells will be deselected.

It would be nice if the RadScheduler allows dragging of multiple selected appointments and change the events'  start time in correspondence with the active appointment offset time.

Currently, the control lacks such support and when this culture is used an exception is thrown. To reproduce use the sample project and press the navigator's Next button several times.

StackTrace:

System.ArgumentOutOfRangeException occurred

  HResult=-2146233086
  Message=Year, Month, and Day parameters describe an un-representable DateTime.
  Source=mscorlib
  StackTrace:
       at System.DateTime.DateToTicks(Int32 year, Int32 month, Int32 day)
       at Telerik.WinControls.UI.DateHelper.GetEndOfMonth(DateTime date, DateTimeFormatInfo dateTimeFormat)
       at Telerik.WinControls.UI.DateHelper.GetMonthDisplayWeeks(DateTime date, DateTimeFormatInfo dateTimeFormat)
       at Telerik.WinControls.UI.SchedulerNavigatorElement.NavigateBackwards()
       at Telerik.WinControls.UI.SchedulerNavigatorElement.OnNavigateBackwards(Object sender, EventArgs e)
       at Telerik.WinControls.UI.SchedulerNavigatorElement.NavigateButton_Click(Object sender, EventArgs e)
       at System.EventHandler.Invoke(Object sender, EventArgs e)
       at Telerik.WinControls.RadElement.OnClick(EventArgs e)
       at Telerik.WinControls.UI.RadButtonItem.OnClick(EventArgs e)
       at Telerik.WinControls.UI.RadButtonElement.OnClick(EventArgs e)
       at Telerik.WinControls.RadElement.DoClick(EventArgs e)
       at Telerik.WinControls.RadElement.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadItem.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.RaiseRoutedEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadItem.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.RaiseRoutedEvent(RadElement sender, RoutedEventArgs args)
       at Telerik.WinControls.RadElement.DoMouseUp(MouseEventArgs e)
       at Telerik.WinControls.ComponentInputBehavior.OnMouseUp(MouseEventArgs e)
       at Telerik.WinControls.RadControl.OnMouseUp(MouseEventArgs e)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
       at Telerik.WinControls.RadControl.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at SchedulerShamsiTest.Program.Main() in c:\Users\dyordano\Desktop\RadSchedulerFixPersianLocale (1)\SchedulerShamsiTest\Program.cs:line 19
  InnerException: 

Workaround:

Sub New()

    InitializeComponent()
     
    Me.RadScheduler1.ActiveViewType = UI.SchedulerViewType.Week
    AddHandler Me.RadSchedulerNavigator1.SchedulerNavigatorElement.ShowWeekendCheckBox.ToggleStateChanged, AddressOf ToggleStateChanged
End Sub

Private Sub ToggleStateChanged(sender As Object, args As UI.StateChangedEventArgs) 
    Me.RadScheduler1.SchedulerElement.RefreshViewElement()
End Sub

Please refer to the attached gif file and sample project.

Workaround: remove the database restrictions and validate the data in the edit dialog before submitting the new appointment data.

IMPORVE. RadScheduler - improve the selection of the cells into RadScheduler to support Ctrl-key.
This will allow to users to select cells/days with space between them.

CLOSED: The selection in scheduling components should be a single range of two dates in which users can create a single appointment after selected. There would be no purpose in multiple range selection as there are no actions the users can perform with them after selecting.

Use GetMultiDayView().Intervals.Add method to add intervals in multi day view. Set the time to be 0:00.

As an example, if an appointment starts at 12 o'clock on one day and ends at 12 o'clock on the next day, it should be positioned to start in the middle of the first day cell and end in the middle of the next day, instead of filling both days.

Currently RadScheduler sets the start date to be the first day of the current week in day view. RadScheduler should allow users to change this behavior in order to show the full month.