How can i use "WaitAliasesChild" method on WPF object?

Hi,

To wait for WPF objects, you can use the special WaitWPFObject method. For example:

Aliases["FusionDesktop"]["HwndSource_MainWindow"]["MainWindow"]["Grid"]["WaitWPFObject"]("BusyMessageControl", 1000)

Also, I recommend that you read the Waiting for an Object, Process or Window Activation online article.