title: Insert characters into a string in C#
body: <p>Given the following string in C#, how would I insert a character in between each character in the string?</p>
  
  <p>For example:
  <code>"Hello Sunshine"</code>
  would become
  <code>"H.e.l.l.o. .S.u.n.s.h.i.n.e"</code></p>
  
  <p>What is the most efficient, fastest way of doing this in C#?</p>