The string is correct but you have been confused by the debugger display which inserts escape characters.
Dump your string to the console and you'll see that it's ok.
Try
string s = '"' + "hello" + '"' + " " + '"' + "!" + '"';
Console.WriteLine(s);
The Console will show
"hello" "!"
and the debugger will show
"\"hello\" \"!\""
Alan.