For this you need to seach in google with keyword
"escape sequence for double quotes"
I can explain you with example you can make changes as per your need
Consider i need string as => My friend told "being late is better than never"
so now to add this string to variable
string str = "My friend told" +"\"being late is better than never\"";
StringBuffer strBuf = new StringBuffer();
strBuf.Append(str);
Where \ is used to escape the next character to it.
Hope this helps you
Cheers