UFT Pro (LeanFT) .NET SDK Reference, Version 14.03
WaitUntil Method
Example 
Waits until a certain condition is met in the specified boolean function or the timeout elapses. When a WaitUntil step runs, it passes the specified test object to the function. This method is useful for synchronizing your test with your application.
Overload List
OverloadDescription
WaitUntil<T>(T,Func<T,Boolean>)Waits until a certain condition is met in the specified boolean function or the timeout elapses. When a WaitUntil step runs, it passes the specified test object to the function. This method is useful for synchronizing your test with your application.  
WaitUntil<T>(T,Func<T,Boolean>,Int32)Waits until a certain condition is met in the specified boolean function or the timeout elapses. When a WaitUntil step runs, it passes the specified test object to the function. This method is useful for synchronizing your test with your application.  
Example
suggestions.WaitUntil(suggestionsBox => suggestionsBox.Exists() && suggestionsBox.IsVisible);