Double quotes in c# doesn't allow multiline

e.g.

string str = "{\"aps\":{\"alert\":\"" + title + "" + message + "\"}}";

I need to make it as for readability:

 string str = "
 {
   \"aps\":
         {
             \"alert\":\"" + title + "" + message + "\"
         }
 }";

How to achieve this, please suggest.