How to work with Test Advantage for WPF Controls ?

While working with Test Advantage and Net Advantage (Infragistics)  for WPF 
controls in QTP/UFT ,we some time get error message  "Object reference not 
set to an instance of obejct"while running the script.

This error message basically thrown by QTP/UFT when "Click" and  "Set" operation 
performed on "WpfButton" and "WpfEdit" objects respectively . This is because operations
are performed over them are not compatible wtih QTP/UFT tool.

How to overcome this issue ?

We can to use 'type' operation over WpfButton and WpfEdit objects. For click operation 
we need to pass "{micAppKey }" and for "Set" operation we need to pass just text .
Demonstration has been done below  :
 
WpfWindow("WpfWindow_AppMainScreen").WpfButton("WpfButton_Submit").Click

WpfWindow("WpfWindow_MainScreen").WpfButton("WpfButton_Submit").type "{micAppKey }"

WpfWindow("WpfWindow_AppMainScreen").WpfEdit("WpfEdit_Name").Set "Mike"

WpfWindow("WpfWindow_AppMainScreen").WpfEdit("WpfEdit_Name").type "Mike"