Converting a TimeSpan to String and Back?

I would like to Convert a TimeSpan to a string, Use the new Save() method to save it to storage when the game is saved. Then Retrieve that string from storage with the new Program() method when the game is loaded again and convert it back into a TimeSpan.
I know that TimeSpan can be converted into a string with Convert.ToString(TimeSpanHere).
How do I convert that string Back into a TimeSpan?