Very strange behavior for the Event:Parameter of Collection Widget

Hi , 

If you set MashupParameterBindings to Collection,for exampe: { "description": "theDesc" },  then the Collection will has a mashup parameter called Event:Description .   

I bind the Event:Description to a express with auto evaluate and hope it can reflect the change of the paramter,  but I feel very confused about the behavior. 

In the inner mashup, I bind the new value to a expression and bind the expression's output to the mashup paramter, what I observed is: 

• If click via a button then the mashup parameter get changed but the Event:Description's binding expression is not triggered
• If click via a value display then mashup parameter get changed and Event:Description's binding expression is triggered , but it always reflect the previous value .  If you check the debug info you'll see a data change event is triggered before the value display's click event , although the click event is the first action you performed. 

Please try the attached xml file to reproduce the strange behavior: 

1. Input value to New Value field in any cell on the left screen, then click "Button",  you'll see the upper text box get changed but the new description on the right screen doesn't change.

2. This time input value to New Value then click "Click" , repeat twice , you'll see the New description on the right screen always display the previous value . 

Is it a bug or designed behavior ? 

Regards,

Sean