I want to add audible driving directions to my application developed on ArcGIS runtime SDK.
Have a look to this https://github.com/Esri/arcgis-runtime-demos-dotnet/tree/master/src/TurnByTurn demo. Especially SayMessageControl on Windows Phone project.
ArcGIS RunTime does not have it but in every Window installation SAPI.DLL is installed and that can be used to create a very fundamental voice by text. Below is a picture a very simple VB.Net project, I am using the SAPI.DLL reference to early bind but I also include the late binding technique. The program will simply "Say" what is in the text box. I have it as a sub, but could be easily incorporated within a class/object.