A Command is a function with an extra 
    
    
    
    
    
    
    
    
    
    
    
    
canExecute observable property to determine
whether the command can be executed.  When executed, a Command function will check the
value of canExecute and throw if false.
This type describes an interface and is not intended to be instantiated directly.
See createCommand to create a command from a function.
    Members
- 
    afterExecute : Event
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    Gets an event which is raised after the command executes, the event is raised with the return value of the command as its only parameter.- 
    
    
    
    
    
    
    
    
    
    Default Value:
    
 undefined
- 
    beforeExecute : Event
- 
    
    Gets an event which is raised before the command executes, the event is raised with an object containing two properties: acancelproperty, which if set to false by the listener will prevent the command from being executed, and anargsproperty, which is the array of arguments being passed to the command.- 
    
    
    
    
    
    
    
    
    
    Default Value:
    
 undefined
- 
    
    Gets whether this command can currently be executed. This property is observable.- 
    
    
    
    
    
    
    
    
    
    Default Value:
    
 undefined
