PostCommandId equals UNDO

[Anonymous]

Hello friends I have big question. When I want to sign PostcommandId equals UNDO = 33032, I have an exception:

"The Revit command id cannot be assigned a command binding." but when I sign another command there is not happen any exceptions. Why is happened to this command? And how to do it right? This is my code:

First decision:

RevitCommandId commandId = RevitCommandId.LookupPostableCommandId(PostableCommand.Undo);
AddInCommandBinding importBinding = a.CreateAddInCommandBinding(commandId); (An exception occurs here)
importBinding.BeforeExecuted += new EventHandler<Autodesk.Revit.UI.Events.BeforeExecutedEventArgs>(Undo);

Second  decision: 

RevitCommandId commandId = RevitCommandId.LookupCommandId("ID_BUTTON_UNDO");
AddInCommandBinding importBinding = a.CreateAddInCommandBinding(commandId); (An exception occurs here)
importBinding.BeforeExecuted += new EventHandler<Autodesk.Revit.UI.Events.BeforeExecutedEventArgs>(Undo);

[jeremytammik]

Maybe Undo is an exception, intentionally?

What does CanPostCommand report for Undo?

[Sean_Page · Accepted solution]

I would suggest that you check to make sure that it can have a binding before trying to add an event handler.

if(commandId.CanHaveBinding)
{
    AddInCommandBinding importBinding = a.CreateAddInCommandBinding(commandId);
}