Value cannot be null. Parameter name: key

[Toxic]

I have a data bound radscheduler. For which I have created a timeslotcontextmenu eg. Add Appointment and set to postback.

However, everytime I click on the context menu I get the above error with the following stack trace :
 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.ArgumentNullException: Value cannot be null.
Parameter name: key

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[ArgumentNullException: Value cannot be null. Parameter name: key] System.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument) +44 System.Collections.Generic.Dictionary`2.FindEntry(TKey key) +7457569 System.Collections.Generic.Dictionary`2.TryGetValue(TKey key, TValue& value) +16 Telerik.Web.UI.RadScheduler.ProcessTimeSlotContextMenuItemCommand(SchedulerPostBackEvent postBack) +106 Telerik.Web.UI.RadScheduler.ProcessPostBackCommand(SchedulerPostBackEvent postBack) +4638 Telerik.Web.UI.RadScheduler.RaisePostBackEvent(String eventArgument) +108 Telerik.Web.UI.RadScheduler.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +39 System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13 System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +175 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565

All other changes to the schedule work fine (moving dates etc.) but the context menu click just comes up with thie error everytime and I cannot understand why.

Please help!

[Toxic]

I have resolved this. I decided to carry on with the coding and noticed I was missing a return value for the item clicked!!!

That was the NULL valued key required, the value of the radmenuitem. This obviously cannot be left blank.

Simple if you think about it.

Tox