From this article you can learn how to insert a string in a string builder by specifying the start position and the text that you need to insert. If you need to insert at the end of the string builder object by using Append() .
sb = new StringBuilder("How to configure connection string in web config?");
sb.Insert(0, "Question 1:");
see the below output the text was inserted at the first position of the string builder.
Question 1:How to configure connection string in web config?Answer: http://infinetsoft.com/Post/How-to-configure-connection-string-in-web-config/1