[NullReferenceException: Object reference not set to an instance of an object.] Telerik.Web.UI.TreeListItemDecorator.PrepareDataItemsServiceCells(RadTreeList owner) +534 Telerik.Web.UI.RadTreeList.PrepareRows() +215 Telerik.Web.UI.RadTreeList.Render(HtmlTextWriter writer) +29 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +208 System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +8 System.Web.UI.Control.Render(HtmlTextWriter writer) +10 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +208 System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +8 System.Web.DynamicData.DynamicControl.Render(HtmlTextWriter writer) +154 ...

Here is the code:

//get the "Room" resource associated with the time slot

var currentRoom = slot.get_resource();

//get all appointments for this "room" in the specified period

var appointmentsForThisRoom = getAppointmentsInRangeByResource(scheduler, start, end, currentRoom, appointment);

//if the list of appointments is not empty there are other appointments in this slot

return appointmentsForThisRoom.get_count() > 0;

}

function warnIfOccupied(start, end, sender, args)

{

var slot = args.get_targetSlot();

var appointment = args.get_appointment();

if (isRoomOccupied(sender, start, end, slot, appointment))

{

alert(

"This room is not available in this time period.");

args.set_cancel(

true);

}

appointment.get_element().style.border =

"";

}

function onAppointmentResizeEnd(sender, args)

{

var start = args.get_appointment().get_start();

var end = args.get_targetSlot().get_endTime();

warnIfOccupied(start, end, sender, args);

}

function onAppointmentMoveEnd(sender, args)

{

var start = args.get_targetSlot().get_startTime();

var end = new Date(start.getTime() + args.get_appointment().get_duration());

warnIfOccupied(start, end, sender, args);

}

function onAppointmentInserting(sender, args)

{

var slot = args.get_targetSlot();

var start = slot.get_startTime();

var end = slot.get_endTime();

if (isRoomOccupied(sender, start, end, slot))

{

alert(

"This room is not available in this time period.");

args.set_cancel(

true);

}

}

<

telerik:RadScheduler runat="server" ID="RadScheduler1" OnClientAppointmentEditing="AppointmentEditing"

OnClientAppointmentInserting="AppointmentInserting" EnableCustomAttributeEditing="true"

SelectedDate="2009-07-26" DataSourceID="EventsDataSource" DataKeyField="MeetingID"

DataSubjectField="Description" DataStartField="Start" DataEndField="End" SelectedView="WeekView"

FirstDayOfWeek="Sunday" LastDayOfWeek="Saturday" Skin="Vista" ShowResourceHeaders="false"

CustomAttributeNames="Description,HostedBy,Room" Height="100%" Localization-ConfirmDeleteText="Are you sure you want to delete this meeting?"

TimelineView-UserSelectable="false" OnClientAppointmentMoveEnd="onAppointmentMoveEnd"

OnClientAppointmentResizeEnd="onAppointmentResizeEnd">

<ResourceTypes>

<telerik:ResourceType KeyField="Room" Name="Room" TextField="Room" ForeignKeyField="Room"

DataSourceID="RoomsDataSource" />

</ResourceTypes>

<AppointmentTemplate>

<div style="color: Maroon;">

<%

#Eval("Description")%></div>

<%

-- <br />--%>

<div style="color: Teal;">

</font>Host:&nbsp;<%#Eval("HostedBy")%></div>

<%

-- <br />--%>

<div style="color: Fuchsia;">

Room:

&nbsp;<%#Eval("Room")%></div>

</AppointmentTemplate>

</telerik:RadScheduler>

<asp:Button ID="btnGo" runat="server" Text="Go" Visible="false" />

<asp:SqlDataSource ID="SqlDataSource1" runat="server"></asp:SqlDataSource>

<asp:SqlDataSource ID="EventsDataSource" runat="server" ProviderName="System.Data.SqlClient"

ConnectionString="<%$ ConnectionStrings:MCHPEVENTS %>" SelectCommand="SELECT [MeetingID], [Description], [Start], [End], [Room], [HostedBy], [Food], [Beverages], [Projector], [Easel], [Flipchart], [Microphone], [HotelAVSupplies], [Comments] FROM [Meetings]"

InsertCommand="INSERT INTO [Meetings] ([Description], [Start], [End], [Room]) VALUES (@Description, @Start, @End, @Room)"

UpdateCommand="UPDATE [Meetings] SET [Description] = @Description, [Start] = @Start, [End] = @End, [Room] = @Room WHERE (MeetingID = @MeetingID)"

DeleteCommand="DELETE FROM [Meetings] WHERE [MeetingID] = @MeetingID">

<DeleteParameters>

<asp:Parameter Name="MeetingID" Type="Int32" />

</DeleteParameters>

<UpdateParameters>

<asp:Parameter Name="MeetingID" Type="Int32" />

<asp:Parameter Name="Description" Type="String" />

<asp:Parameter Name="Start" Type="DateTime" />

<asp:Parameter Name="End" Type="DateTime" />

<asp:Parameter Name="Room" Type="String" />

</UpdateParameters>

<InsertParameters>

<asp:Parameter Name="Description" Type="String" />

<asp:Parameter Name="Start" Type="DateTime" />

<asp:Parameter Name="End" Type="DateTime" />

<asp:Parameter Name="Room" Type="String" DefaultValue="TBD" />

</InsertParameters>

</asp:SqlDataSource>

<asp:SqlDataSource ID="RoomsDataSource" runat="server" ProviderName="System.Data.SqlClient"

ConnectionString="<%$ ConnectionStrings:MCHPEVENTS %>" SelectCommand="SELECT DISTINCT([Room]) FROM [Meetings]">

</asp:SqlDataSource>