" 转义字符， a系统警报，逐字字符串(verbatim string)

 string str="The key factors are "focus" and "perseverance"";

 string str = "All finished. a";

string str = @"This world is fair
and everything can exist must be reasonable
Everything depend on myself.Devote myself into .net and coding.Spare no efforts on work.
Stay focused and keep shipping.";